SELECT * FROM article WHERE uid = (SELECT uid FROM user WHERE status=1 ORDER BY uid DESC LIMIT 1)
SELECT * FROM t1 WHERE column1 = (SELECT MAX(column2) FROM t2)
SELECT * FROM article AS t WHERE 2 = (SELECT COUNT(*) FROM article WHERE article.uid = t.uid)
SELECT * FROM article WHERE uid IN(SELECT uid FROM user WHERE status=1)
SELECT s1 FROM table1 WHERE s1 > ANY (SELECT s2 FROM table2)
SELECT s1 FROM table1 WHERE s1 > ALL (SELECT s2 FROM table2)
NOT IN 是 <> ALL 的别名，二者相同 。
特殊情况
如果 table2 为空表，则 ALL 后的结果为 TRUE；
如果子查询返回如 (0,NULL,1) 这种尽管 s1 比返回结果都大，但有空行的结果，则 ALL 后的结果为 UNKNOWN 。
SELECT s1 FROM table1 WHERE s1 > (SELECT s2 FROM table2)
SELECT s1 FROM table1 WHERE s1 > ALL (SELECT MAX(s1) FROM table2)
3. MySQL 行子查询：
指子查询返回的结果集是一行 N 列，该子查询的结果通常是对表的某行数据进行查询而返回的结果集 。
例子：
SELECT * FROM table1 WHERE (1,2) = (SELECT column1, column2 FROM table2)
注：(1,2) 等同于 row(1,2)
SELECT * FROM article WHERE (title,content,uid) = (SELECT title,content,uid FROM blog WHERE bid=2)
4. MySQL 表子查询：
指子查询返回的结果集是 N 行 N 列的一个表数据 。
例子：
SELECT * FROM article WHERE (title,content,uid) IN (SELECT title,content,uid FROM blog)
select table1.customer_id,city,count(order_id)
from table1join table2
on table1.customer_id=table2.customer_id
where table1.customer_id<>'tx' and table1.customer_id<>'9you'
group by customer_id
having count(order_id) >
any (
select count(order_id)
from table2
where customer_id='tx' or customer_id='9you'
group by customer_id);
select order_id
from table2
where customer_idin
(select customer_id
from table1
where city='hangzhou');
sql语句2：获得城市为hangzhou，并且存在订单的用户 。
select *
from table1
where city='hangzhou' and exists
(select *
from table2
where table1.customer_id=table2.customer_id);
SELECT * FROM t1
WHERE t1.a1 NOTin (SELECT a2 FROM t2 )
优化后：
SELECT * FROM t1
LEFT JOIN t2 ON t1.a1=t2.a2
WHERE t2.a2 IS NULL
例子2：
SELECT * FROM article WHERE (title,content,uid) IN (SELECT title,content,uid FROM blog)
优化后：
SELECT * FROM article
innerjoin blog
on (article.title=blog.title AND article.content=blog.content AND article.uid=blog.uid)
