1：SALES表的表数据如下：

需求：请写出可以得到以下的结果SQL

建表语句:

create table sales(year int ,month string,amt int);
insert into sales values
(2021,'04',100),
(2021,'05',200),
(2020,'04',400),
(2020,'05',150),
(2019,'04',300),
(2019,'05',null),
(2020,'04',50);

分析思路:要实现行转列无非就是===>>>带条件的聚合

--行转列套路===>>>带条件的聚合
select year,
       sum(if(month='04',amt,0)) as amt4,
       sum(if(month='05',amt,0)) as amt5,
       sum(amt) as sum_all

最终SQL:

--行转列的常规套路就是group by+带条件(case when或if)的聚合
select year,
       amt4, amt5, sum_all,
       round((amt5-amt4)/amt4,4)*100 || '%'  as rate
       from
(select year,
       sum(if(month='04',amt,0)) as amt4,
       sum(if(month='05',amt,0)) as amt5,
       sum(amt) as sum_all
from sales group by  year) t;

 结果: