MySQL 查询结果取交集的实现方法

1
mysql中如何实现以下sql查询
(select s.name
from student s, transcript t
where s.studid = t.studid and t.crscode = 'cs305')
intersect
(select s.name
from student s, transcript t
where s.studid = t.studid and t.crscode = 'cs315')
请各位不吝赐教，小弟先谢过~
解：
取交集
select a.* from
(
select s.name
from student s, transcript t
where s.studid = t.studid and t.crscode = 'cs305'
) as a
cross join
(
select s.name
from student s, transcript t
where s.studid = t.studid and t.crscode = 'cs315'
) as b on a.name = b.name;

2.
select * from (
select distinct col1 from t1 where...
union all
select distinct col1 from t1 where...
) as tbl
group by tbl.col1 having count(*) = 2

3.
交集：
select * from table1 as a join table2 as b on a.name =b.name
举例：
表a:
fielda
001
002
003
表b:
fielda
001
002
003
004
请教如何才能得出以下结果集，即表a, b行交集
fielda
001
002
003
答案：select a.fielda from a inner join b on a.fielda=b.fielda
差集：
not in 表示差集
select * from table1 where name not in (select name from table2)