版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/lnazj/article/details/84111573
1.嵌套再进行连接查询
SELECT * from (
SELECT * from tit_training_program
WHERE level_id=#{levelId}) as p
LEFT JOIN(
select * from tit_training_user
where user_id=#{userId}) as u
ON p.id=u.program_id
2.查询本周内的数据
SELECT
SUM(integral),
DAYOFWEEK(create_time),
case(DAYOFWEEK(create_time))
when 1 then '星期天'
when 2 then '星期一'
when 3 then '星期二'
when 4 then '星期三'
when 5 then '星期四'
when 6 then '星期五'
when 7 then '星期六'
else '' end
FROM
tik_integral_detail
WHERE
YEARWEEK(
date_format(create_time, '%Y-%m-%d')
) = YEARWEEK(now())
group by Date(create_time)
3.将一个表中的数据批量不重复地导入到另一个表
insert b select * from a where not exists(select 1 from b where id=a.id)