Mysql 子查询的执行

Question

假设我有这样的查询

SELECT DISTINCT customer_name 
FROM borrower 
WHERE customer_name in (SELECT customer_name FROM depositor)

我们可以将以上视为两个查询

一个

SELECT DISTINCT customer_name 
FROM borrower 
WHERE customer_name

B

SELECT customer_name 
FROM depositor

哪个先执行？这个规则对所有子查询都一样吗？

我们可以写什么类型的子查询？给我一些开始使用教程链接的指示。

Answer 1

编辑，因为第一个答案是错误的。但是解释是正确的:|

A 首先执行。当子查询相关时，应用上面显示的“所有”子查询。

+----+--------------------+-----------+----------------+---------------+---------------+---------+------+------+----------+--------------------------+
| id | select_type        | table     | type           | possible_keys | key           | key_len | ref  | rows | filtered | Extra                    |
+----+--------------------+-----------+----------------+---------------+---------------+---------+------+------+----------+--------------------------+
|  1 | PRIMARY            | borrower  | index          | NULL          | customer_name | 52      | NULL |    6 |   100.00 | Using where; Using index |
|  2 | DEPENDENT SUBQUERY | depositor | index_subquery | customer_name | customer_name | 52      | func |    1 |   100.00 | Using index              |
+----+--------------------+-----------+----------------+---------------+---------------+---------+------+------+----------+--------------------------+

顺便说一句。 MySQL 6 将消除此问题，并且两个查询的选择类型都将变为 PRIMARY。参见 1