mysql 嵌套使用

原文链接

1. SELECT语句的子查询:

语法：SELECT ... FROM 表1 WHERE 列1 =
(SELECT ... FROM ... WHERE ....)

2.SELECT语句的表查询

语法：SELECT ... FROM (SELECT....) AS TEMP_TABLE WHERE ...

注意：这里面有个注意，就是列名不能重复！有些人会出现：

#1060 - Duplicate column name '列名' 错误，这个就是列名重复了

解决方案：去掉一个列名。

PS：这个和MSSQL别名有点不一样，

select * from (SELECT * FROM a) b

3.条件关联关系查询：
语法：便于查看我缩进下代码

SELECT col1 FROM t1 AS a

WHERE a.col1 = (SELECT col1 FROM b AS a
WHERE a.col1 = ( SELECT col1 FROM c
WHERE a.col2 = c.col1

)

);

4.SELECT (SELECT s1 FROM t2) FROM t1;
5.SELECT (SELECT s2 FROM t1);