one day two donkeys got bored.they wanted to live a comfortable life,so the ...in today’s world,you need a reason to laugh.so let’s find it in humor times. ...
先说ex**ts 英文存在的意思, 父查询where not ex**ts(子查询)---不存在子查询则满足父查询出发条件,where 字段 not in(子查询),如 select * from表名 where 学号 not in(select学号from表名where成绩60的人的信息,,----------不知道我举得例子你看明白没