有关于SQL语句的问题

select * from course
where name in (select name from course where CName in('数学','物理','语文') group by name having count(*)=3)
and name not in(select name from course group by name having count(*)>3)

谁可以帮我解说下这句的我意思，最好分段说明~谢谢了

select name from course where CName in('数学','物理','语文') group by name having count(*)=3这一段子查询语句，首先将'数学','物理','语文'三门科目名称分组（group by name ）然后统计出各科的数量，并将科目数量等于3的筛选出来，select name from course group by name having count(*)>3)这也是一个子查询，它没有指定要分组的科目，默认是根据所有的科目分组，并将科目数量大于3的科目排除掉。

select name,CName from course where CName = '数学' and name in (select name from course where CName = '物理' or CName = '语文') union all select name,CName from course where CName = '物理' and name in (select name from course where CName = '数学' or CName = '语文') union all select name,CName from course where CName = '语文' and name in (select name from course where CName = '数学' or CName = '物理') 经过测试可以达到你要的效果 如果可以谢谢采纳

select name from course where CName in('数学','物理','语文') group by name having count(*)=3

从表course中取出name字段，条件是：CName的值为‘数学’或者‘物理’或者‘语文’，同时，查询出的记录要有3个相同的name。

如：

name Cname

123 数学

123 数学

123 物理

select * from course where name in （）

从course中取出所有字段，条件是：name在上面已经取出的name集合中。

select * from course 查询所有信息，在course表里

where name in (select name from course where CName in('数学','物理','语文') group by name having count(*)=3)

嵌套查询，姓名是（从course表里查找姓名，选择的课程名是“'数学','物理','语文'”，按姓名分组，且课程名出现次数为3次）

and name not in(select name from course group by name having count(*)>3)

且（嵌套查询）（姓名在course表里出现3次以上）就不添加进去