mysql 日环比统计

接到一个任务，要计算日环比的情况。

16、查询销售额日环比情况

日环比：（今日-昨日）/ 昨日的一个比率情况。

1，建表

DROP TABLE IF EXISTS sale;
create table sale(
  id int not null AUTO_INCREMENT,
  record_date date,
  ammount int default 0,
  primary key(id)
);

2，插入数据

INSERT INTO sale VALUES
(1, '2020-01-01', 1000),
(2, '2020-01-02', 2500),
(3, '2020-01-03', 2000),
(4, '2020-01-04', 3000),
(5, '2020-01-05', 2900),
(6, '2020-01-06', 3100),
(7, '2020-01-07', 3300);

3，sql

1，关联查询的方式：

 SELECT 
 cur.record_date,
 cur.ammount AS current_ammount, 
 pre.ammount AS previous_ammount,  
 (cur.ammount - pre.ammount) AS diffValue,
 (cur.ammount - pre.ammount)/ pre.ammount AS daily_growth_rate
 FROM sale cur, sale pre
 WHERE cur.record_date = DATE_ADD(pre.record_date, INTERVAL 1 DAY);
 -- 或者用
 -- WHERE 1 = DATEDIFF(cur.record_date, pre.record_date);

2，用变量的方式：

错误位置：

-- 放在赋值后面，就跟当天比了，公式变成： （当天 - 昨天 )/当天
SELECT *, (@diff:=ammount-@pre) AS diffValue,@pre:=ammount AS pre,
(@diff / @pre) AS daily_growth_rate 
FROM  sale ORDER BY record_date;

正确位置：

-- 要放前面，但是还是有一个问题，会有第一条，没有去除， 这个麻烦些，还得去除第一条 
SELECT *, (@diff:=ammount-@pre) AS diffValue,
 (@diff / @pre) AS daily_growth_rate, 
  @pre:=ammount AS pre 
FROM  sale ORDER BY record_date;

第一条也算进去了。跟最后一条进行相比较了。

去除第一条：

SELECT record_date, ammount AS current_ammount, 
pre AS previous_ammount, daily_growth_rate
FROM (
SELECT *, (@diff:=ammount-@pre) AS diffValue,
 (@diff / @pre) AS daily_growth_rate, 
  @pre:=ammount AS pre 
FROM  sale ORDER BY record_date
) AS temp WHERE record_date 
NOT IN (SELECT MIN(record_date) min_record_date FROM sale);