Evernewss的博客

1. 题1873 if(employee_id % 2 = 1,(if(name like 'M%',0,salary)),0) AS bonus name like 'M%' 可用 left(name,1) 2. 题627 update salary set sex = if(sex = 'm','f','m') 3. 题196 delete from Person where Id not in ( select * from( select min(Id)

1. 题1448 GROUP_CONCAT(DISTINCT PRODUCT) AS products 多列压缩 select sell_date,count(distinct product) AS num_sold,GROUP_CONCAT(DISTINCT PRODUCT) AS products from Activities group by sell_date 输入： Activities 表： +------------+-------------+ | sell_date | prod