MySQL

SQL 基础

DDL 语句

show databases;
show tables;
desc table_name; # 获取表信息
show create table 表名; // 查询指定表的建表语句 

数据类型

char(10) 不满10个会用空格填充，性能好一点
varchar(10) 变长字符串，性能差一点

CREATE TABLE table_employee(
    id int,
    eno char(10) comment '工号',
    ename varchar(10) comment '姓名',
    sex char(1) comment '性别',
    age tinyint unsigned comment '年龄',
    identification_card char(18) comment '身份证号',
    join_time date comment '入职时间'
) comment '员工表';

Leetcode

返回第N高的薪水

CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
declare M INT;
  set M = N-1;
  RETURN (
      # Write your MySQL query statement below.
    select distinct salary from Employee order by salary desc
     limit M, 1 
  );
END