sql特殊用法: 查询添加, 查询更新, 添加或更新

1. insert select语句: 查询添加

sql完成数据查询并入功能:

INSERT INTO `temp`(`vid`, `vcount`) 
select vid, sum(vcount) from log where date > '2020-04-23' GROUP BY vid;

2. insert update语句: 查询更新

sql完成数据查询并更新功能:

update video t1
	set t1.vcount= t1.vcount + (
	select vcount from temp_video t2 
	where t2.vid=t1.vid
)

3. insert on duplicate key update语句: 添加或更新

sql数据存在则更新,不存在就添加功能:

INSERT INTO t_user(id, name, age) VALUES (20, 'hello', 12)
ON DUPLICATE KEY UPDATE name='repeat';