本文主要演示sqlite数据库 增删改查创建数据库以及数据库表的基本操作，仅供学习参考。
一、sqlite数据库操作类封装：
sql\database.h
sql\database.cc
// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SQL_DATABASE_H_
#define SQL_DATABASE_H_
#include <stddef.h>
#include <stdint.h>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
#include <optional>
#include "base/component_export.h"
#include "base/containers/flat_map.h"
#include "base/dcheck_is_on.h"
#include "base/feature_list.h"
#include "base/files/file_path.h"
#include "base/functional/callback.h"
#include "base/gtest_prod_util.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ptr_exclusion.h"
#include "base/memory/ref_counted.h"
#include "base/sequence_checker.h"
#include "base/strings/string_piece.h"
#include "base/threading/scoped_blocking_call.h"
#include "base/types/pass_key.h"
#include "sql/internal_api_token.h"
#include "sql/sql_features.h"
#include "sql/sqlite_result_code.h"
#include "sql/sqlite_result_code_values.h"
#include "sql/statement_id.h"
// Forward declaration for SQLite structures. Headers in the public sql:: API
// must NOT include sqlite3.h.
struct sqlite3;
struct sqlite3_file;
struct sqlite3_stmt;
namespace base::trace_event {
class ProcessMemoryDump;
} // namespace base::trace_event
namespace perfetto::protos::pbzero {
class ChromeSqlDiagnostics;
}
namespace sql {
class DatabaseMemoryDumpProvider;
class Recovery;
class Statement;
namespace test {
class ScopedErrorExpecter;
} // namespace test
struct COMPONENT_EXPORT(SQL) DatabaseOptions {
// Default page size for newly created databases.
//
// Guaranteed to match SQLITE_DEFAULT_PAGE_SIZE.
static constexpr int kDefaultPageSize = 4096;
// If true, the database can only be opened by one process at a time.
//
// SQLite supports a locking protocol that allows multiple processes to safely
// operate on the same database at the same time. The locking protocol is used
// on every transaction, and comes with a small performance penalty.
//
// Setting this to true causes the locking protocol to be used once, when the
// database is opened. No other SQLite process will be able to access the
// database at the same time. Note that this uses OS-level
// advisory/cooperative locking, so this does not protect the database file
// from uncooperative processes.
//
// More details at https://www.sqlite.org/pragma.html#pragma_locking_mode
//
// SQLite's locking protocol is summarized at
// https://www.sqlite.org/c3ref/io_methods.html
//
// Exclusive mode is strongly recommended. It reduces the I/O cost of setting
// up a transaction. It also removes the need of handling transaction failures
// due to lock contention.
bool exclusive_locking = true;
// If true, enables exclusive=true vfs URI parameter on the database file.
// This is only supported on Windows.
//
// If this option is true then the database file cannot be opened by any
// processes on the system until the database has been closed. Note, this is
// not the same as `exclusive_locking` above, which refers to
// advisory/cooperative locks. This option sets file handle sharing attributes
// to prevent the database files from being opened from any process including
// being opened a second time by the hosting process.
//
// A side effect of setting this flag is that the database cannot be
// preloaded. If you would like to set this flag on a preloaded database,
// please reach out to a //sql owner.
//
// This option is experimental and will be merged into the `exclusive_locking`
// option above if proven to cause no OS compatibility issues.
// TODO(crbug.com/1429117): Merge into above option, if possible.
bool exclusive_database_file_lock = false;
// If true, enables SQLite's Write-Ahead Logging (WAL).
//
// WAL integration is under development, and should not be used in shipping
// Chrome features yet. In particular, our custom database recovery code does
// not support the WAL log file.
//
// WAL mode is currently not fully supported on FuchsiaOS. It will only be
// turned on if the database is also using exclusive locking mode.
// (https://crbug.com/1082059)
//
// Note: Changing page size is not supported when in WAL mode. So running
// 'PRAGMA page_size = <new-size>' will result in no-ops.
//
// More details at https://www.sqlite.org/wal.html
bool wal_mode =
base::FeatureList::IsEnabled(sql::features::kEnableWALModeByDefault);
// If true, transaction commit waits for data to reach persistent media.
//
// This is currently only meaningful on macOS. All other operating systems
// only support flushing directly to disk.
//
// If both `flush_to_media` and `wal_mode` are false, power loss can lead to
// database corruption.
//
// By default, SQLite considers that transactions commit when they reach the
// disk controller's memory. This guarantees durability in the event of
// software crashes, up to and including the operating system. In the event of
// power loss, SQLite may lose data. If `wal_mode` is false (SQLite uses a
// rollback journal), power loss can lead to database corruption.
//
// When this option is enabled, committing a transaction causes SQLite to wait
// until the data is written to the persistent media. This guarantees
// durability in the event of power loss, which is needed to guarantee the
// integrity of non-WAL databases.
bool flush_to_media = false;
// Database page size.
//
// New Chrome features should set an explicit page size in their
// DatabaseOptions initializers, even if they use the default page size. This
// makes it easier to track the page size used by the databases on the users'
// devices.
//
// The value in this option is only applied to newly created databases. In
// other words, changing the value doesn't impact the databases that have
// already been created on the users' devices. So, changing the value in the
// code without a lot of work (re-creating existing databases) will result in
// inconsistent page sizes across the fleet of user devices, which will make
// it (even) more difficult to reason about database performance.
//
// Larger page sizes result in shallower B-trees, because they allow an inner
// page to hold more keys. On the flip side, larger page sizes may result in
// more I/O when making small changes to existing records.
//
// Must be a power of two between 512 and 65536 inclusive.
//
// TODO(pwnall): Replace the default with an invalid value after all
// sql::Database users explicitly initialize page_size.
int page_size = kDefaultPageSize;
// The size of in-memory cache, in pages.
//
// New Chrome features should set an explicit cache size in their
// DatabaseOptions initializers, even if they use the default cache size. This
// makes it easier to track the cache size used by the databases on the users'
// devices. The default page size of 4,096 bytes results in a cache size of
// 500 pages.
//
// SQLite's database cache will take up at most (`page_size` * `cache_size`)
// bytes of RAM.
//
// 0 invokes SQLite's default, which is currently to size up the cache to use
// exactly 2,048,000 bytes of RAM.
//
// TODO(pwnall): Replace the default with an invalid value after all
// sql::Database users explicitly initialize page_size.
int cache_size = 0;
// Stores mmap failures in the SQL schema, instead of the meta table.
//
// This option is strongly discouraged for new databases, and will eventually
// be removed.
//
// If this option is true, the mmap status is stored in the database schema.
// Like any other schema change, changing the mmap status invalidates all
// pre-compiled SQL statements.
bool mmap_alt_status_discouraged = false;
// If true, enables SQL views (a discouraged feature) for this database.
//
// The use of views is discouraged for Chrome code. See README.md for details
// and recommended replacements.
//
// If this option is false, CREATE VIEW and DROP VIEW succeed, but SELECT
// statements targeting views fail.
bool enable_views_discouraged = false;
// If true, enables virtual tables (a discouraged feature) for this database.
//
// The use of virtual tables is discouraged for Chrome code. See README.md for
// details and recommended replacements.
//
// If this option is false, CREATE VIRTUAL TABLE and DROP VIRTUAL TABLE
// succeed, but statements targeting virtual tables fail.
bool enable_virtual_tables_discouraged = false;
};
// Holds database diagnostics in a structured format.
struct COMPONENT_EXPORT(SQL) DatabaseDiagnostics {
DatabaseDiagnostics();
~DatabaseDiagnostics();
using TraceProto = perfetto::protos::pbzero::ChromeSqlDiagnostics;
// Write a representation of this object into tracing proto.
void WriteIntoTrace(perfetto::TracedProto<TraceProto> context) const;
// This was the original error code that triggered the error callback. Should
// generally match `error_code`, but this isn't guaranteed by the code.
int reported_sqlite_error_code = 0;
// Corresponds to `Database::GetErrorCode()`.
int error_code = 0;
// Corresponds to `Database::GetLastErrno()`.
int last_errno = 0;
// Corresponds to `Statement::GetSQLStatement()` of the problematic statement.
// This doesn't include the bound values, and therefore is free of any PII.
std::string sql_statement;
// The 'version' value stored in the user database's meta table, if it can be
// read. If we fail to read the version of the user database, it's left as 0.
int version = 0;
// Most rows in 'sql_schema' have a non-NULL 'sql' column. Those rows' 'sql'
// contents are logged here, one element per row.
std::vector<std::string> schema_sql_rows;
// Some rows of 'sql_schema' have a NULL 'sql' column. They are typically
// autogenerated indices, like "sqlite_autoindex_downloads_slices_1". These
// are also logged here by their 'name' column, one element per row.
std::vector<std::string> schema_other_row_names;
// Sanity checks used for all errors.
bool has_valid_header = false;
bool has_valid_schema = false;
// Corresponds to `Database::GetErrorMessage()`.
std::string error_message;
};
// Handle to an open SQLite database.
//
// Instances of this class are not thread-safe. After construction, a Database
// instance should only be accessed from one sequence.
//
// When a Database instance goes out of scope, any uncommitted transactions are
// rolled back.
class COMPONENT_EXPORT(SQL) Database {
private:
class StatementRef; // Forward declaration, see real one below.
public:
// Creates an instance that can receive Open() / OpenInMemory() calls.
//
// Some `options` members are only applied to newly created databases.
//
// Most operations on the new instance will fail until Open() / OpenInMemory()
// is called.
explicit Database(DatabaseOptions options);
// This constructor is deprecated.
//
// When transitioning away from this default constructor, consider setting
// DatabaseOptions::explicit_locking to true. For historical reasons, this
// constructor results in DatabaseOptions::explicit_locking set to false.
//
// TODO(crbug.com/1126968): Remove this constructor after migrating all
// uses to the explicit constructor below.
Database();
Database(const Database&) = delete;
Database& operator=(const Database&) = delete;
Database(Database&&) = delete;
Database& operator=(Database&&) = delete;
~Database();
// Allows mmapping to be disabled globally by default in the calling process.
// Must be called before any threads attempt to create a Database.
//
// TODO(crbug.com/1117049): Remove this global configuration.
static void DisableMmapByDefault();
// Pre-init configuration ----------------------------------------------------
// The page size that will be used when creating a new database.
int page_size() const { return options_.page_size; }
// Returns whether a database will be opened in WAL mode.
bool UseWALMode() const;
// Opt out of memory-mapped file I/O.
void set_mmap_disabled() { mmap_disabled_ = true; }
// Set an error-handling callback. On errors, the error number (and
// statement, if available) will be passed to the callback.
//
// If no callback is set, the default error-handling behavior is invoked. The
// default behavior is to LOGs the error and propagate the failure.
//
// In DCHECK-enabled builds, the default error-handling behavior currently
// DCHECKs on errors. This is not correct, because DCHECKs are supposed to
// cover invariants and never fail, whereas SQLite errors can surface even on
// correct usage, due to I/O errors and data corruption. At some point in the
// future, errors will not result in DCHECKs.
//
// The callback will be called on the sequence used for database operations.
// The callback will never be called after the Database instance is destroyed.
using ErrorCallback = base::RepeatingCallback<void(int, Statement*)>;
void set_error_callback(ErrorCallback callback) {
DCHECK(!callback.is_null()) << "Use reset_error_callback() explicitly";
DCHECK(error_callback_.is_null())
<< "Overwriting previously set error callback";
error_callback_ = std::move(callback);
}
void reset_error_callback() { error_callback_.Reset(); }
bool has_error_callback() const { return !error_callback_.is_null(); }
// Developer-friendly database ID used in logging output and memory dumps.
void set_histogram_tag(const std::string& histogram_tag) {
DCHECK(!is_open());
histogram_tag_ = histogram_tag;
}
const std::string& histogram_tag() const { return histogram_tag_; }
// Asks SQLite to perform a full integrity check on the database.
//
// Returns true if the integrity check was completed successfully. Success
// does not necessarily entail that the database is healthy. Finding
// corruption and reporting it in `messages` counts as success.
//
// If the method returns true, `messages` is populated with a list of
// diagnostic messages. If the integrity check finds no errors, `messages`
// will contain exactly one "ok" string. This unusual API design is explained
// by the fact that SQLite exposes integrity check functionality as a PRAGMA,
// and the PRAGMA returns "ok" in case of success.
bool FullIntegrityCheck(std::vector<std::string>* messages);
// Meant to be called from a client error callback so that it's able to
// get diagnostic information about the database. `diagnostics` is an optional
// out parameter. If `diagnostics` is defined, this method populates all of
// its fields.
std::string GetDiagnosticInfo(int extended_error,
Statement* statement,
DatabaseDiagnostics* diagnostics = nullptr);
// Reports memory usage into provided memory dump with the given name.
bool ReportMemoryUsage(base::trace_event::ProcessMemoryDump* pmd,
const std::string& dump_name);
// Initialization ------------------------------------------------------------
// Opens or creates a database on disk.
//
// `db_file_path` points to the file storing database pages. Other files
// associated with the database (rollback journal, write-ahead log,
// shared-memory file) may be created.
//
// Returns true in case of success, false in case of failure.
[[nodiscard]] bool Open(const base::FilePath& db_file_path);
// Alternative to Open() that creates an in-memory database.
//
// Returns true in case of success, false in case of failure.
//
// The memory associated with the database will be released when the database
// is closed.
[[nodiscard]] bool OpenInMemory();
// Alternative to Open() that creates a temporary on-disk database.
//
// Returns true in case of success, false in case of failure.
//
// The files associated with the temporary database will be deleted when the
// database is closed.
[[nodiscard]] bool OpenTemporary(base::PassKey<Recovery>);
// Returns true if the database has been successfully opened.
bool is_open() const;
// Closes the database. This is automatically performed on destruction for
// you, but this allows you to close the database early. You must not call
// any other functions after closing it. It is permissable to call Close on
// an uninitialized or already-closed database.
void Close();
// Hints the file system that the database will be accessed soon.
//
// This method should be called on databases that are on the critical path to
// Chrome startup. Informing the filesystem about our expected access pattern
// early on reduces the likelihood that we'll be blocked on disk I/O. This has
// a high impact on startup time.
//
// This method should not be used for non-critical databases. While using it
// will likely improve micro-benchmarks involving one specific database,
// overuse risks randomizing the disk I/O scheduler, slowing down Chrome
// startup.
void Preload();
// Release all non-essential memory associated with this database connection.
void TrimMemory();
// Raze the database to the ground. This approximates creating a
// fresh database from scratch, within the constraints of SQLite's
// locking protocol (locks and open handles can make doing this with
// filesystem operations problematic). Returns true if the database
// was razed.
//
// false is returned if the database is locked by some other
// process.
//
// NOTE(shess): Raze() will DCHECK in the following situations:
// - database is not open.
// - the database has a transaction open.
// - a SQLite issue occurs which is structural in nature (like the
// statements used are broken).
// Since Raze() is expected to be called in unexpected situations,
// these all return false, since it is unlikely that the caller
// could fix them.
//
// The database's page size is taken from |options_.page_size|. The
// existing database's |auto_vacuum| setting is lost (the
// possibility of corruption makes it unreliable to pull it from the
// existing database). To re-enable on the empty database requires
// running "PRAGMA auto_vacuum = 1;" then "VACUUM".
//
// NOTE(shess): For Android, SQLITE_DEFAULT_AUTOVACUUM is set to 1,
// so Raze() sets auto_vacuum to 1.
//
// TODO(shess): Raze() needs a database so cannot clear SQLITE_NOTADB.
// TODO(shess): Bake auto_vacuum into Database's API so it can
// just pick up the default.
bool Raze();
// Breaks all outstanding transactions (as initiated by
// BeginTransaction()), closes the SQLite database, and poisons the
// object so that all future operations against the Database (or
// its Statements) fail safely, without side effects.
//
// This is intended as an alternative to Close() in error callbacks.
// Close() should still be called at some point.
void Poison();
// `Raze()` the database and `Poison()` the handle. Returns the return
// value from `Raze()`.
bool RazeAndPoison();
// Delete the underlying database files associated with |path|. This should be
// used on a database which is not opened by any Database instance. Open
// Database instances pointing to the database can cause odd results or
// corruption (for instance if a hot journal is deleted but the associated
// database is not).
//
// Returns true if the database file and associated journals no
// longer exist, false otherwise. If the database has never
// existed, this will return true.
static bool Delete(const base::FilePath& path);
// Transactions --------------------------------------------------------------
// Transaction management. We maintain a virtual transaction stack to emulate
// nested transactions since sqlite can't do nested transactions. The
// limitation is you can't roll back a sub transaction: if any transaction
// fails, all transactions open will also be rolled back. Any nested
// transactions after one has rolled back will return fail for Begin(). If
// Begin() fails, you must not call Commit or Rollback().
//
// Normally you should use sql::Transaction to manage a transaction, which
// will scope it to a C++ context.
bool BeginTransaction();
void RollbackTransaction();
bool CommitTransaction();
// Rollback all outstanding transactions. Use with care, there may
// be scoped transactions on the stack.
void RollbackAllTransactions();
bool HasActiveTransactions() const {
DCHECK_GE(transaction_nesting_, 0);
return transaction_nesting_ > 0;
}
// Deprecated in favor of HasActiveTransactions().
//
// Returns the current transaction nesting, which will be 0 if there are
// no open transactions.
int transaction_nesting() const { return transaction_nesting_; }
// Attached databases---------------------------------------------------------
// Attaches an existing database to this connection.
//
// `attachment_point` must only contain lowercase letters.
//
// Attachment APIs are only exposed for use in recovery. General use is
// discouraged in Chrome. The README has more details.
//
// On the SQLite version shipped with Chrome (3.21+, Oct 2017), databases can
// be attached while a transaction is opened. However, these databases cannot
// be detached until the transaction is committed or aborted.
bool AttachDatabase(const base::FilePath& other_db_path,
base::StringPiece attachment_point,
InternalApiToken);
// Detaches a database that was previously attached with AttachDatabase().
//
// `attachment_point` must match the argument of a previously successsful
// AttachDatabase() call.
//
// Attachment APIs are only exposed for use in recovery. General use is
// discouraged in Chrome. The README has more details.
bool DetachDatabase(base::StringPiece attachment_point, InternalApiToken);
// Statements ----------------------------------------------------------------
// Executes a SQL statement. Returns true for success, and false for failure.
//
// `sql` should be a single SQL statement. Production code should not execute
// multiple SQL statements at once, to facilitate crash debugging. Test code
// should use ExecuteScriptForTesting().
//
// `sql` cannot have parameters. Statements with parameters can be handled by
// sql::Statement. See GetCachedStatement() and GetUniqueStatement().
[[nodiscard]] bool Execute(const char* sql);
// Executes a sequence of SQL statements.
//
// Returns true if all statements execute successfully. If a statement fails,
// stops and returns false. Calls should be wrapped in ASSERT_TRUE().
//
// The database's error handler is not invoked when errors occur. This method
// is a convenience for setting up a complex on-disk database state, such as
// an old schema version with test contents.
[[nodiscard]] bool ExecuteScriptForTesting(const char* sql_script);
// Returns a statement for the given SQL using the statement cache. It can
// take a nontrivial amount of work to parse and compile a statement, so
// keeping commonly-used ones around for future use is important for
// performance.
//
// The SQL_FROM_HERE macro is the recommended way of generating a StatementID.
// Code that generates custom IDs must ensure that a StatementID is never used
// for different SQL statements. Failing to meet this requirement results in
// incorrect behavior, and should be caught by a DCHECK.
//
// The SQL statement passed in |sql| must match the SQL statement reported
// back by SQLite. Mismatches are caught by a DCHECK, so any code that has
// automated test coverage or that was manually tested on a DCHECK build will
// not exhibit this problem. Mismatches generally imply that the statement
// passed in has extra whitespace or comments surrounding it, which waste
// storage and CPU cycles.
//
// If the |sql| has an error, an invalid, inert StatementRef is returned (and
// the code will crash in debug). The caller must deal with this eventuality,
// either by checking validity of the |sql| before calling, by correctly
// handling the return of an inert statement, or both.
//
// Example:
// sql::Statement stmt(database_.GetCachedStatement(
// SQL_FROM_HERE, "SELECT * FROM foo"));
// if (!stmt)
// return false; // Error creating statement.
scoped_refptr<StatementRef> GetCachedStatement(StatementID id,
const char* sql);
// Used to check a |sql| statement for syntactic validity. If the statement is
// valid SQL, returns true.
bool IsSQLValid(const char* sql);
// Returns a non-cached statement for the given SQL. Use this for SQL that
// is only executed once or only rarely (there is overhead associated with
// keeping a statement cached).
//
// See GetCachedStatement above for examples and error information.
scoped_refptr<StatementRef> GetUniqueStatement(const char* sql);
// Returns a non-cached statement same as `GetUniqueStatement()`, except
// returns an invalid statement if the statement makes direct changes to the
// database file. This readonly check does not include changes made by
// application-defined functions. See more at:
// https://www.sqlite.org/c3ref/stmt_readonly.html.
scoped_refptr<Database::StatementRef> GetReadonlyStatement(const char* sql);
// Performs a passive checkpoint on the main attached database if it is in
// WAL mode. Returns true if the checkpoint was successful and false in case
// of an error. It is a no-op if the database is not in WAL mode.
//
// Note: Checkpointing is a very slow operation and will block any writes
// until it is finished. Please use with care.
bool CheckpointDatabase();
// Info querying -------------------------------------------------------------
// Returns true if the given structure exists. Instead of test-then-create,
// callers should almost always prefer the "IF NOT EXISTS" version of the
// CREATE statement.
bool DoesIndexExist(base::StringPiece index_name);
bool DoesTableExist(base::StringPiece table_name);
bool DoesViewExist(base::StringPiece table_name);
// Returns true if a column with the given name exists in the given table.
//
// Calling this method on a VIEW returns an unspecified result.
//
// This should only be used by migration code for legacy features that do not
// use MetaTable, and need an alternative way of figuring out the database's
// current version.
bool DoesColumnExist(const char* table_name, const char* column_name);
// Returns sqlite's internal ID for the last inserted row. Valid only
// immediately after an insert.
int64_t GetLastInsertRowId() const;
// Returns sqlite's count of the number of rows modified by the last
// statement executed. Will be 0 if no statement has executed or the database
// is closed.
int64_t GetLastChangeCount();
// Approximates the amount of memory used by SQLite for this database.
//
// This measures the memory used for the page cache (most likely the biggest
// consumer), database schema, and prepared statements.
//
// The memory used by the page cache can be recovered by calling TrimMemory(),
// which will cause SQLite to drop the page cache.
int GetMemoryUsage();
// Errors --------------------------------------------------------------------
// Returns the error code associated with the last sqlite operation.
int GetErrorCode() const;
// Returns the errno associated with GetErrorCode(). See
// SQLITE_LAST_ERRNO in SQLite documentation.
int GetLastErrno() const;
// Returns a pointer to a statically allocated string associated with the
// last sqlite operation.
const char* GetErrorMessage() const;
// Return a reproducible representation of the schema equivalent to
// running the following statement at a sqlite3 command-line:
// SELECT type, name, tbl_name, sql FROM sqlite_schema ORDER BY 1, 2, 3, 4;
std::string GetSchema();
// Returns |true| if there is an error expecter (see SetErrorExpecter), and
// that expecter returns |true| when passed |error|. Clients which provide an
// |error_callback| should use IsExpectedSqliteError() to check for unexpected
// errors; if one is detected, DLOG(DCHECK) is generally appropriate (see
// OnSqliteError implementation).
static bool IsExpectedSqliteError(int sqlite_error_code);
// Computes the path of a database's rollback journal.
//
// The journal file is created at the beginning of the database's first
// transaction. The file may be removed and re-created between transactions,
// depending on whether the database is opened in exclusive mode, and on
// configuration options. The journal file does not exist when the database
// operates in WAL mode.
//
// This is intended for internal use and tests. To preserve our ability to
// iterate on our SQLite configuration, features must avoid relying on
// the existence of specific files.
static base::FilePath JournalPath(const base::FilePath& db_path);
// Computes the path of a database's write-ahead log (WAL).
//
// The WAL file exists while a database is opened in WAL mode.
//
// This is intended for internal use and tests. To preserve our ability to
// iterate on our SQLite configuration, features must avoid relying on
// the existence of specific files.
static base::FilePath WriteAheadLogPath(const base::FilePath& db_path);
// Computes the path of a database's shared memory (SHM) file.
//
// The SHM file is used to coordinate between multiple processes using the
// same database in WAL mode. Thus, this file only exists for databases using
// WAL and not opened in exclusive mode.
//
// This is intended for internal use and tests. To preserve our ability to
// iterate on our SQLite configuration, features must avoid relying on
// the existence of specific files.
static base::FilePath SharedMemoryFilePath(const base::FilePath& db_path);
// Internal state accessed by other classes in //sql.
sqlite3* db(InternalApiToken) const { return db_; }
bool poisoned(InternalApiToken) const { return poisoned_; }
base::FilePath DbPath(InternalApiToken) const { return DbPath(); }
// Interface with sql::test::ScopedErrorExpecter.
using ScopedErrorExpecterCallback = base::RepeatingCallback<bool(int)>;
static void SetScopedErrorExpecter(ScopedErrorExpecterCallback* expecter,
base::PassKey<test::ScopedErrorExpecter>);
static void ResetScopedErrorExpecter(
base::PassKey<test::ScopedErrorExpecter>);
private:
// Statement accesses StatementRef which we don't want to expose to everybody
// (they should go through Statement).
friend class Statement;
FRIEND_TEST_ALL_PREFIXES(SQLDatabaseTest, CachedStatement);
FRIEND_TEST_ALL_PREFIXES(SQLDatabaseTest, CollectDiagnosticInfo);
FRIEND_TEST_ALL_PREFIXES(SQLDatabaseTest, ComputeMmapSizeForOpen);
FRIEND_TEST_ALL_PREFIXES(SQLDatabaseTest, ComputeMmapSizeForOpenAltStatus);
FRIEND_TEST_ALL_PREFIXES(SQLDatabaseTest, OnMemoryDump);
FRIEND_TEST_ALL_PREFIXES(SQLDatabaseTest, RegisterIntentToUpload);
FRIEND_TEST_ALL_PREFIXES(SQLiteFeaturesTest, WALNoClose);
FRIEND_TEST_ALL_PREFIXES(SQLEmptyPathDatabaseTest, EmptyPathTest);
// Enables a special behavior for OpenInternal().
enum class OpenMode {
// No special behavior.
kNone = 0,
// Retry if the database error handler is invoked and closes the database.
// Database error handlers that call RazeAndPoison() take advantage of this.
kRetryOnPoision = 1,
// Open an in-memory database. Used by OpenInMemory().
kInMemory = 2,
// Open a temporary database. Used by OpenTemporary().
kTemporary = 3,
};
// Implements Open(), OpenInMemory(), and OpenTemporary().
//
// `db_file_path` is a UTF-8 path to the file storing the database pages. The
// path must be empty if `mode` is kTemporary. The path must be the SQLite
// magic memory path string if `mode` is kMemory.
bool OpenInternal(const std::string& file_name, OpenMode mode);
// Configures the underlying sqlite3* object via sqlite3_db_config().
//
// To minimize the number of possible SQLite code paths executed in Chrome,
// this method must be called right after the underlying sqlite3* object is
// obtained from sqlite3_open*(), before any other sqlite3_*() methods are
// called on the object.
void ConfigureSqliteDatabaseObject();
// Internal close function used by Close() and RazeAndPoison().
// |forced| indicates that orderly-shutdown checks should not apply.
void CloseInternal(bool forced);
// Construct a ScopedBlockingCall to annotate IO calls, but only if
// database wasn't open in memory. ScopedBlockingCall uses |from_here| to
// declare its blocking execution scope (see https://www.crbug/934302).
void InitScopedBlockingCall(
const base::Location& from_here,
std::optional<base::ScopedBlockingCall>* scoped_blocking_call) const {
if (!in_memory_)
scoped_blocking_call->emplace(from_here, base::BlockingType::MAY_BLOCK);
}
// Internal helper for Does*Exist() functions.
bool DoesSchemaItemExist(base::StringPiece name, base::StringPiece type);
// Used to implement the interface with sql::test::ScopedErrorExpecter.
static ScopedErrorExpecterCallback* current_expecter_cb_;
// A StatementRef is a refcounted wrapper around a sqlite statement pointer.
// Refcounting allows us to give these statements out to sql::Statement
// objects while also optionally maintaining a cache of compiled statements
// by just keeping a refptr to these objects.
//
// A statement ref can be valid, in which case it can be used, or invalid to
// indicate that the statement hasn't been created yet, has an error, or has
// been destroyed.
//
// The Database may revoke a StatementRef in some error cases, so callers
// should always check validity before using.
class COMPONENT_EXPORT(SQL) StatementRef
: public base::RefCounted<StatementRef> {
public:
REQUIRE_ADOPTION_FOR_REFCOUNTED_TYPE();
// |database| is the sql::Database instance associated with
// the statement, and is used for tracking outstanding statements
// and for error handling. Set to nullptr for invalid refs.
// |stmt| is the actual statement, and should only be null
// to create an invalid ref. |was_valid| indicates whether the
// statement should be considered valid for diagnostic purposes.
// |was_valid| can be true for a null |stmt| if the Database has
// been forcibly closed by an error handler.
StatementRef(Database* database, sqlite3_stmt* stmt, bool was_valid);
StatementRef(const StatementRef&) = delete;
StatementRef& operator=(const StatementRef&) = delete;
StatementRef(StatementRef&&) = delete;
StatementRef& operator=(StatementRef&&) = delete;
// When true, the statement can be used.
bool is_valid() const { return !!stmt_; }
// When true, the statement is either currently valid, or was
// previously valid but the database was forcibly closed. Used
// for diagnostic checks.
bool was_valid() const { return was_valid_; }
// If we've not been linked to a database, this will be null.
Database* database() const { return database_; }
// Returns the sqlite statement if any. If the statement is not active,
// this will return nullptr.
sqlite3_stmt* stmt() const { return stmt_; }
// Destroys the compiled statement and sets it to nullptr. The statement
// will no longer be active. |forced| is used to indicate if
// orderly-shutdown checks should apply (see Database::RazeAndPoison()).
void Close(bool forced);
// Construct a ScopedBlockingCall to annotate IO calls, but only if
// database wasn't open in memory. ScopedBlockingCall uses |from_here| to
// declare its blocking execution scope (see https://www.crbug/934302).
void InitScopedBlockingCall(
const base::Location& from_here,
std::optional<base::ScopedBlockingCall>* scoped_blocking_call) const {
if (database_)
database_->InitScopedBlockingCall(from_here, scoped_blocking_call);
}
private:
friend class base::RefCounted<StatementRef>;
~StatementRef();
raw_ptr<Database> database_;
raw_ptr<sqlite3_stmt> stmt_;
bool was_valid_;
};
friend class StatementRef;
// Executes a rollback statement, ignoring all transaction state. Used
// internally in the transaction management code.
void DoRollback();
// Called by a StatementRef when it's being created or destroyed. See
// open_statements_ below.
void StatementRefCreated(StatementRef* ref);
void StatementRefDeleted(StatementRef* ref);
// Used by sql:: internals to report a SQLite error related to this database.
//
// `sqlite_error_code` contains the error code reported by SQLite. Possible
// values are documented at https://www.sqlite.org/rescode.html
//
// `statement` is non-null if the error is associated with a sql::Statement.
// Otherwise, `sql_statement` will be a non-null string pointing to a
// statically-allocated (valid for the entire duration of the process) buffer
// pointing to either a SQL statement or a SQL comment (starting with "-- ")
// pointing to a "sqlite3_" function name.
void OnSqliteError(SqliteErrorCode sqlite_error_code,
Statement* statement,
const char* sql_statement);
// Like Execute(), but returns a SQLite result code.
//
// This method returns SqliteResultCode::kOk or a SQLite error code. In other
// words, it never returns SqliteResultCode::{kDone, kRow}.
//
// This method is only exposed to the Database implementation. Code that uses
// sql::Database should not be concerned with SQLite result codes.
[[nodiscard]] SqliteResultCode ExecuteAndReturnResultCode(const char* sql);
// Like |Execute()|, but retries if the database is locked.
[[nodiscard]] bool ExecuteWithTimeout(const char* sql,
base::TimeDelta ms_timeout);
// Implementation helper for GetUniqueStatement() and GetCachedStatement().
scoped_refptr<StatementRef> GetStatementImpl(const char* sql,
bool is_readonly);
// Release page-cache memory if memory-mapped I/O is enabled and the database
// was changed. Passing true for |implicit_change_performed| allows
// overriding the change detection for cases like DDL (CREATE, DROP, etc),
// which do not participate in the total-rows-changed tracking.
void ReleaseCacheMemoryIfNeeded(bool implicit_change_performed);
// Returns the results of sqlite3_db_filename(), which should match the path
// passed to Open().
base::FilePath DbPath() const;
// Helper to collect diagnostic info for a corrupt database.
std::string CollectCorruptionInfo();
// Helper to collect diagnostic info for errors. `diagnostics` is an optional
// out parameter. If `diagnostics` is defined, this method populates SOME of
// its fields. Some of the fields are left unmodified for the caller.
std::string CollectErrorInfo(int sqlite_error_code,
Statement* stmt,
DatabaseDiagnostics* diagnostics) const;
// The size of the memory mapping that SQLite should use for this database.
//
// The return value follows the semantics of "PRAGMA mmap_size". In
// particular, zero (0) means memory-mapping should be disabled, and the value
// is capped by SQLITE_MAX_MMAP_SIZE. More details at
// https://www.sqlite.org/pragma.html#pragma_mmap_size
//
// "Memory-mapped access" is usually shortened to "mmap", which is the name of
// the POSIX system call used to implement. The same principles apply on
// Windows, but its more-descriptive API names don't make for good shorthands.
//
// When mmap is enabled, SQLite attempts to use the memory-mapped area (by
// calling xFetch() in the VFS file API) instead of requesting a database page
// buffer from the pager and reading (via xRead() in the VFS API) into it.
// When this works out, the database page cache ends up only storing pages
// whose contents has been modified. More details at
// https://sqlite.org/mmap.html
//
// I/O errors on memory-mapped files result in crashes in Chrome. POSIX
// systems signal SIGSEGV or SIGBUS on I/O errors in mmap-ed files. Windows
// raises the EXECUTE_IN_PAGE_ERROR strucuted exception in this case. Chrome
// does not catch signals or structured exceptions.
//
// In order to avoid crashes, this method attempts to read the file using
// regular I/O, and returns 0 (no mmap) if it encounters any error.
size_t ComputeMmapSizeForOpen();
// Helpers for ComputeMmapSizeForOpen().
bool GetMmapAltStatus(int64_t* status);
bool SetMmapAltStatus(int64_t status);
// sqlite3_prepare_v3() flags for this database.
int SqlitePrepareFlags() const;
// Returns a SQLite VFS interface pointer to the file storing database pages.
//
// Returns null if the database is not backed by a VFS file. This is always
// the case for in-memory databases. Temporary databases (only used by sq
// ::Recovery) start without a backing VFS file, and only get a file when they
// outgrow their page cache.
//
// This method must only be called while the database is successfully opened.
sqlite3_file* GetSqliteVfsFile();
// Will eventually be checked on all methods. See https://crbug.com/1306694
SEQUENCE_CHECKER(sequence_checker_);
// The actual sqlite database. Will be null before Init has been called or if
// Init resulted in an error.
// This field is not a raw_ptr<> because it was filtered by the rewriter for:
// #addr-of
RAW_PTR_EXCLUSION sqlite3* db_ = nullptr;
// TODO(shuagga@microsoft.com): Make `options_` const after removing all
// setters.
DatabaseOptions options_;
// Holds references to all cached statements so they remain active.
//
// flat_map is appropriate here because the codebase has ~400 cached
// statements, and each statement is at most one insertion in the map
// throughout a process' lifetime.
base::flat_map<StatementID, scoped_refptr<StatementRef>> statement_cache_;
// A list of all StatementRefs we've given out. Each ref must register with
// us when it's created or destroyed. This allows us to potentially close
// any open statements when we encounter an error.
std::set<StatementRef*> open_statements_;
// Number of currently-nested transactions.
int transaction_nesting_ = 0;
// True if any of the currently nested transactions have been rolled back.
// When we get to the outermost transaction, this will determine if we do
// a rollback instead of a commit.
bool needs_rollback_ = false;
// True if database is open with OpenInMemory(), False if database is open
// with Open().
bool in_memory_ = false;
// |true| if the Database was closed using RazeAndPoison(). Used
// to enable diagnostics to distinguish calls to never-opened
// databases (incorrect use of the API) from calls to once-valid
// databases.
bool poisoned_ = false;
// |true| if SQLite memory-mapped I/O is not desired for this database.
bool mmap_disabled_;
// |true| if SQLite memory-mapped I/O was enabled for this database.
// Used by ReleaseCacheMemoryIfNeeded().
bool mmap_enabled_ = false;
// Used by ReleaseCacheMemoryIfNeeded() to track if new changes have happened
// since memory was last released.
int64_t total_changes_at_last_release_ = 0;
// Called when a SQLite error occurs.
//
// This callback may be null, in which case errors are handled using a default
// behavior.
//
// This callback must never be exposed outside this Database instance. This is
// a straight-forward way to guarantee that this callback will not be called
// after the Database instance goes out of scope. set_error_callback() makes
// this guarantee.
ErrorCallback error_callback_;
// Developer-friendly database ID used in logging output and memory dumps.
std::string histogram_tag_;
// Stores the dump provider object when db is open.
std::unique_ptr<DatabaseMemoryDumpProvider> memory_dump_provider_;
};
} // namespace sql
#endif // SQL_DATABASE_H_
二、sqlite数据库查询和事务处理类：
sql\statement.h
sql\statement.cc
// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SQL_STATEMENT_H_
#define SQL_STATEMENT_H_
#include <stdint.h>
#include <string>
#include <vector>
#include "base/component_export.h"
#include "base/containers/span.h"
#include "base/dcheck_is_on.h"
#include "base/memory/ref_counted.h"
#include "base/sequence_checker.h"
#include "base/strings/string_piece.h"
#include "base/thread_annotations.h"
#include "base/time/time.h"
#include "sql/database.h"
namespace sql {
enum class SqliteResultCode : int;
// Possible return values from ColumnType in a statement. These should match
// the values in sqlite3.h.
enum class ColumnType {
kInteger = 1,
kFloat = 2,
kText = 3,
kBlob = 4,
kNull = 5,
};
// Compiles and executes SQL statements.
//
// This class is not thread-safe. An instance must be accessed from a single
// sequence. This is enforced in DCHECK-enabled builds.
//
// Normal usage:
// sql::Statement s(connection_.GetUniqueStatement(...));
// s.BindInt(0, a);
// if (s.Step())
// return s.ColumnString(0);
//
// If there are errors getting the statement, the statement will be inert; no
// mutating or database-access methods will work. If you need to check for
// validity, use:
// if (!s.is_valid())
// return false;
//
// Step() and Run() just return true to signal success. If you want to handle
// specific errors such as database corruption, install an error handler in
// in the connection object using set_error_delegate().
class COMPONENT_EXPORT(SQL) Statement {
public:
// Creates an uninitialized statement. The statement will be invalid until
// you initialize it via Assign.
Statement();
explicit Statement(scoped_refptr<Database::StatementRef> ref);
Statement(const Statement&) = delete;
Statement& operator=(const Statement&) = delete;
Statement(Statement&&) = delete;
Statement& operator=(Statement&&) = delete;
~Statement();
// Initializes this object with the given statement, which may or may not
// be valid. Use is_valid() to check if it's OK.
void Assign(scoped_refptr<Database::StatementRef> ref);
// Resets the statement to an uninitialized state corresponding to
// the default constructor, releasing the StatementRef.
void Clear();
// Returns true if the statement can be executed. All functions can still
// be used if the statement is invalid, but they will return failure or some
// default value. This is because the statement can become invalid in the
// middle of executing a command if there is a serious error and the database
// has to be reset.
bool is_valid() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return ref_->is_valid();
}
// Running -------------------------------------------------------------------
// Executes the statement, returning true on success. This is like Step but
// for when there is no output, like an INSERT statement.
bool Run();
// Executes the statement, returning true if there is a row of data returned.
// You can keep calling Step() until it returns false to iterate through all
// the rows in your result set.
//
// When Step returns false, the result is either that there is no more data
// or there is an error. This makes it most convenient for loop usage. If you
// need to disambiguate these cases, use Succeeded().
//
// Typical example:
// while (s.Step()) {
// ...
// }
// return s.Succeeded();
bool Step();
// Resets the statement to its initial condition. This includes any current
// result row, and also the bound variables if the |clear_bound_vars| is true.
void Reset(bool clear_bound_vars);
// Returns true if the last executed thing in this statement succeeded. If
// there was no last executed thing or the statement is invalid, this will
// return false.
bool Succeeded() const;
// Binding -------------------------------------------------------------------
// These all take a 0-based parameter index and return true on success.
// strings there may be out of memory.
void BindNull(int param_index);
void BindBool(int param_index, bool val);
void BindInt(int param_index, int val);
void BindInt(int param_index,
int64_t val) = delete; // Call BindInt64() instead.
void BindInt64(int param_index, int64_t val);
void BindDouble(int param_index, double val);
void BindCString(int param_index, const char* val);
void BindString(int param_index, base::StringPiece val);
// If you need to store (potentially invalid) UTF-16 strings losslessly,
// store them as BLOBs instead. `BindBlob()` has an overload for this purpose.
void BindString16(int param_index, base::StringPiece16 value);
void BindBlob(int param_index, base::span<const uint8_t> value);
// Overload that makes it easy to pass in std::string values.
void BindBlob(int param_index, base::span<const char> value) {
BindBlob(param_index, base::as_bytes(base::make_span(value)));
}
// Overload that makes it easy to pass in std::u16string values.
void BindBlob(int param_index, base::span<const char16_t> value) {
BindBlob(param_index, base::as_bytes(base::make_span(value)));
}
// Conforms with base::Time serialization recommendations.
//
// This is equivalent to the following snippets, which should be replaced.
// * BindInt64(col, val.ToInternalValue())
// * BindInt64(col, val.ToDeltaSinceWindowsEpoch().InMicroseconds())
//
// Features that serialize base::Time in other ways, such as ToTimeT() or
// InMillisecondsSinceUnixEpoch(), will require a database migration to be
// converted to this (recommended) serialization method.
//
// TODO(crbug.com/1195962): Migrate all time serialization to this method, and
// then remove the migration details above.
void BindTime(int param_index, base::Time time);
// Conforms with base::TimeDelta serialization recommendations.
//
// This is equivalent to the following snippets, which should be replaced.
// * BindInt64(col, delta.ToInternalValue())
// * BindInt64(col, delta.InMicroseconds())
//
// TODO(crbug.com/1402777): Migrate all TimeDelta serialization to this method
// and remove the migration details above.
void BindTimeDelta(int param_index, base::TimeDelta delta);
// Retrieving ----------------------------------------------------------------
// Returns the number of output columns in the result.
int ColumnCount() const;
// Returns the type associated with the given column.
//
// Watch out: the type may be undefined if you've done something to cause a
// "type conversion." This means requesting the value of a column of a type
// where that type is not the native type. For safety, call ColumnType only
// on a column before getting the value out in any way.
ColumnType GetColumnType(int col);
// These all take a 0-based argument index.
bool ColumnBool(int column_index);
int ColumnInt(int column_index);
int64_t ColumnInt64(int column_index);
double ColumnDouble(int column_index);
std::string ColumnString(int column_index);
// If you need to store and retrieve (potentially invalid) UTF-16 strings
// losslessly, store them as BLOBs instead. They may be retrieved with
// `ColumnBlobAsString16()`.
std::u16string ColumnString16(int column_index);
// Conforms with base::Time serialization recommendations.
//
// This is equivalent to the following snippets, which should be replaced.
// * base::Time::FromInternalValue(ColumnInt64(col))
// * base::Time::FromDeltaSinceWindowsEpoch(
// base::Microseconds(ColumnInt64(col)))
//
// TODO(crbug.com/1195962): Migrate all time serialization to this method, and
// then remove the migration details above.
base::Time ColumnTime(int column_index);
// Conforms with base::TimeDelta deserialization recommendations.
//
// This is equivalent to the following snippets, which should be replaced.
// * base::TimeDelta::FromInternalValue(ColumnInt64(column_index))
//
// TODO(crbug.com/1402777): Migrate all TimeDelta serialization to this method
// and remove the migration details above.
base::TimeDelta ColumnTimeDelta(int column_index);
// Returns a span pointing to a buffer containing the blob data.
//
// The span's contents should be copied to a caller-owned buffer immediately.
// Any method call on the Statement may invalidate the span.
//
// The span will be empty (and may have a null data) if the underlying blob is
// empty. Code that needs to distinguish between empty blobs and NULL should
// call GetColumnType() before calling ColumnBlob().
base::span<const uint8_t> ColumnBlob(int column_index);
bool ColumnBlobAsString(int column_index, std::string* result);
bool ColumnBlobAsString16(int column_index, std::u16string* result);
bool ColumnBlobAsVector(int column_index, std::vector<char>* result);
bool ColumnBlobAsVector(int column_index, std::vector<uint8_t>* result);
// Diagnostics --------------------------------------------------------------
// Returns the original text of a SQL statement WITHOUT any bound values.
// Intended for logging in case of failures. Note that DOES NOT return any
// bound values, because that would cause a privacy / PII issue for logging.
std::string GetSQLStatement();
private:
friend class Database;
// Checks SQLite result codes and handles any errors.
//
// Returns `sqlite_result_code`. This gives callers the convenience of writing
// "return CheckSqliteResultCode(sqlite_result_code)" and gives the compiler
// the opportunity of doing tail call optimization (TCO) on the code above.
//
// This method reports error codes to the associated Database, and updates
// internal state to reflect whether the statement succeeded or not.
SqliteResultCode CheckSqliteResultCode(SqliteResultCode sqlite_result_code);
// Should be called by all mutating methods to check that the statement is
// valid. Returns true if the statement is valid. DCHECKS and returns false
// if it is not.
// The reason for this is to handle two specific cases in which a Statement
// may be invalid. The first case is that the programmer made an SQL error.
// Those cases need to be DCHECKed so that we are guaranteed to find them
// before release. The second case is that the computer has an error (probably
// out of disk space) which is prohibiting the correct operation of the
// database. Our testing apparatus should not exhibit this defect, but release
// situations may. Therefore, the code is handling disjoint situations in
// release and test. In test, we're ensuring correct SQL. In release, we're
// ensuring that contracts are honored in error edge cases.
bool CheckValid() const;
// Helper for Run() and Step(), calls sqlite3_step() and returns the checked
// value from it.
SqliteResultCode StepInternal();
// Retrieve and log the count of VM steps required to execute the query.
void ReportQueryExecutionMetrics() const;
// The actual sqlite statement. This may be unique to us, or it may be cached
// by the Database, which is why it's ref-counted. This pointer is
// guaranteed non-null.
scoped_refptr<Database::StatementRef> ref_
GUARDED_BY_CONTEXT(sequence_checker_);
// See Succeeded() for what this holds.
bool succeeded_ GUARDED_BY_CONTEXT(sequence_checker_) = false;
#if DCHECK_IS_ON()
// Used to DCHECK() that Bind*() is called before Step() or Run() are called.
bool step_called_ GUARDED_BY_CONTEXT(sequence_checker_) = false;
bool run_called_ GUARDED_BY_CONTEXT(sequence_checker_) = false;
#endif // DCHECK_IS_ON()
SEQUENCE_CHECKER(sequence_checker_);
};
} // namespace sql
#endif // SQL_STATEMENT_H_
事务处理类
sql\transaction.h
sql\transaction.cc
三、数据库操作演示：
1、demo\BUILD.gn
添加sql依赖
executable("03-sqlclient") {
sources = [
"03-sqlclient/client.cc",
]
if (is_win) {
ldflags = [ "/LARGEADDRESSAWARE" ]
}
deps = [
"//base",
"//sql",
"//build/win:default_exe_manifest",
]
}2、demo\03-sqlclient\client.cc
#include <stdarg.h>
#include <stddef.h>
#include <stdint.h>
#include <windows.h>
#include <iostream>
#include "base/command_line.h"
#include "base/files/file_path.h"
#include "base/files/file_util.h"
#include "base/logging.h"
#include "base/strings/stringprintf.h"
#include "build/build_config.h"
#include "sql/database.h"
#include "sql/statement.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
int main(int argc, const char* argv[]) {
base::CommandLine::Init(argc, argv);
base::FilePath db_path(FILE_PATH_LITERAL("d:/jdtest.db"));
sql::Database db;
// 1、创建数据库
LOG(ERROR)<<"open/create d:/jdtest.db";
if (db.Open(db_path)) {
LOG(INFO) << "open db ok : " << db_path;
if (!db.DoesTableExist("test_tb")) {
// 2、创建表
LOG(ERROR)<<"CRATE TABLE test_tb";
bool is_ok = db.Execute(
"CREATE TABLE test_tb(id INTEGER PRIMARY KEY NOT NULL, name "
"varchar(256), ege int)");
if (!is_ok) {
LOG(ERROR) << "CREATE TABLE test_tb erro";
}
}
// 3、插入数据
LOG(ERROR)<<"INSERT ";
for (int i = 0; i < 10; ++i) {
std::string sql = base::StringPrintf(
"INSERT INTO test_tb(name,ege) VALUES('%s',%d)", "abc", 20 + i);
bool is_ok = db.Execute(sql.c_str());
if (!is_ok) {
LOG(ERROR) << "INSERT INTO test_tb erro";
}
}
// 4、查询数据
LOG(ERROR)<<"SELECT ";
sql::Statement s(db.GetUniqueStatement("SELECT *from test_tb"));
if (s.is_valid()) {
while (s.Step()) {
int id = s.ColumnInt(0);
std::string name = s.ColumnString(1);
int age = s.ColumnInt(2);
LOG(ERROR) << "id :" << id << " name :" << name << " age :" << age;
}
}
// 5、删除数据
LOG(ERROR)<<"DELETE ";
if (!db.Execute("DELETE FROM test_tb WHERE ege >22")) {
LOG(ERROR) << "DELETE FROM test_tberro";
}
} else {
LOG(ERROR) << "open db erro : " << db_path;
}
return 0;
}
3、gn gen out/debug
4、ninja -C out/debug demo:03-sqlclient
四、编译运行之后效果：
![第21课-C++[set和map学习和使用]](https://i-blog.csdnimg.cn/direct/026e251f5f2844618d836c12d9c44469.png)
