Mysql查看优化后的SQL 语句

EXPLAIN  EXTENDED 

1先执行 EXPLAIN  EXTENDED  

2 show warnings；

EXPLAIN  EXTENDED 
SELECT
  *
FROM
  `Test1` d
WHERE d.`ap_id` IN
  (SELECT
    id
  FROM
    ap
  WHERE ap_code IN (
      'Test120190305192721001',
      'Test120190309152839001',
      'Test120190309152904001'
    ));

SHOW WARNINGS;

查看优化后最终执行的sql

  In 并不是走的子查询 而是 join ，这个是 从上面的画红线的地方copy 出来的

SELECT
 `id` AS `id`,
 `ap_id` AS `ap_id`,
 `re_id` AS `re_id`,
 `update_time` AS `update_time`,
 `create_time` AS `create_time`,
 `deleted` AS `deleted`
FROM
 `ap`
  JOIN`Test1` `d`
WHERE (
    (
     `ap_id` =`ap`.`id`
    )
    AND (
     `ap`.`ap_code` IN (
        'Test120190305192721001',
        'Test120190309152839001',
        'Test120190309152904001'
      )
    )
  )

EXPLAIN EXTENDED 
SELECT
d.*
FROM
`Test1` d
INNER JOIN ap a
ON d.`ap_id` = a.id
WHERE a.ap_code IN (
'Test120190305192721001',
'Test120190309152839001',
'Test120190309152904001'
);

查看优化后的sql 

SELECT
 `id` AS `id`,
 `ap_id` AS `ap_id`,
 `re_id` AS `re_id`,
 `update_time` AS `update_time`,
 `create_time` AS `create_time`,
 `deleted` AS `deleted`
FROM
 `Test1` `d`
  JOIN`ap` `a`
WHERE (
    (
     `ap_id` =`a`.`id`
    )
    AND (
     `a`.`ap_code` IN (
        'Test120190305192721001',
        'Test120190309152839001',
        'Test120190309152904001'
      )
    )
  );