Mysql-sql行转列

原始数据如下图所示：（商品的销售明细）
date=业务日期；Item=商品名称；saleqty=销售数量

-- 建立测试数据（表）
create table test (Date varchar(10), item char(10),saleqty int);
insert test values('2010-01-01','AAA',8);
insert test values('2010-01-02','AAA',4);
insert test values('2010-01-03','AAA',5);
insert test values('2010-01-01','BBB',1);
insert test values('2010-01-02','CCC',2);
insert test values('2010-01-03','DDD',6);

实现的方法和思路如下：两个方法

-- 实现结果的静态SQL语句写法
-- 整理报表需要的格式

方法一：case item when x then xx when y then yy end  

select date,
case item when 'AAA' then saleqty end as AAA,
case item when 'BBB' then saleqty end as BBB,
case item when 'CCC' then saleqty end as CCC,
case item when 'DDD' then saleqty end as DDD
from test;

方法二：if(条件判断，成立结果，不成立结果)

select date,
if (item = 'AAA',saleqty,null) as AAA,
if (item = 'BBB',saleqty,null) as BBB,
if (item = 'CCC',saleqty,null) as CCC,
if (item = 'DDD',saleqty,null) as DDD
from test;

-- 按日期汇总行

select date,
sum(case item when 'AAA' then saleqty end)as AAA,
sum(case item when 'BBB' then saleqty end)as BBB,
sum(case item when 'CCC' then saleqty end)as CCC,
sum(case item when 'DDD' then saleqty end)as DDD
from test group by date;

select date,
sum(if (item = 'AAA',saleqty,null)) as AAA,
sum(if (item = 'BBB',saleqty,null)) as BBB,
sum(if (item = 'CCC',saleqty,null)) as CCC,
sum(if (item = 'DDD',saleqty,null)) as DDD
from test group by date;

-- 处理数据：将空值的栏位填入数字0；

select date,
ifnull(sum(case item when 'AAA' then saleqty end) ,0)as AAA,
ifnull(sum(case item when 'BBB' then saleqty end) ,0)as BBB,
ifnull(sum(case item when 'CCC' then saleqty end) ,0)as CCC,
ifnull(sum(case item when 'DDD' then saleqty end) ,0)as DDD
from test group by date;

select date,
ifnull(sum(if (item = 'AAA',saleqty,null)),0) as AAA,
ifnull(sum(if (item = 'BBB',saleqty,null)),0) as BBB,
ifnull(sum(if (item = 'CCC',saleqty,null)),0) as CCC,
ifnull(sum(if (item = 'DDD',saleqty,null)),0) as DDD
from test group by date;

静态SQL语句编写完成！

其实有一步骤有点多余：可以直接if（，，0），而不是if（，，null）

select date,
if (item = 'AAA',saleqty,0) as AAA,
if (item = 'BBB',saleqty,0) as BBB,
if (item = 'CCC',saleqty,0) as CCC,
if (item = 'DDD',saleqty,0) as DDD
from test;

select date,
sum(if (item = 'AAA',saleqty,0)) as AAA,
sum(if (item = 'BBB',saleqty,0)) as BBB,
sum(if (item = 'CCC',saleqty,0)) as CCC,
sum(if (item = 'DDD',saleqty,0)) as DDD
from test group by date;

静态SQL语句编写完成！

参考网址https://www.cnblogs.com/ShaYeBlog/p/3594517.html

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三月的时候就遇到了行转列。

计算一个表中的字段被清洗和标准化被命中的比例和原因。

转成行输出。