SQL语句学习

看似简单，但其实包含很多技巧思维

1.查询课程表中所有科目大于80的学生

select distinct name from student where name not in (select name from student where grade<80);

　这样是错误的

select distinct name from student where name in (select name from student where grade>=80);
这样代表只要有一门大于80即可