Question

我有一个问题，我几个小时都无法解决。

我有3张桌子：

Process

+----+----------+----------------+--------+-------------+---------------+-------------+---------+------+
| id |   name   |  description   | active | responsible | informByEmail | informBySms | remarks | icon |
+----+----------+----------------+--------+-------------+---------------+-------------+---------+------+
|  4 | Process1 | TestDecriptino |      1 |           0 |             0 |           0 | 0       | NULL |
|  5 | Process2 | test           |      0 |           0 |             0 |           0 | test    | NULL |
|  6 | Process3 | 12322          |      1 |           0 |             0 |           0 | 12322   | NULL |
|  7 | Process4 | 222222222222   |      0 |           0 |             0 |           0 | 2222222 | NULL |
|  9 | Process5 | sgdasad        |      1 |           0 |             1 |           0 | dhds    | NULL |
+----+----------+----------------+--------+-------------+---------------+-------------+---------+------+

Systems

+----+---------+-------------+--------+-------------------+---------------+-------------+---------+------+
| id |  name   | description | active | responsibleUserId | informByEmail | informBySms | remarks | icon |
+----+---------+-------------+--------+-------------------+---------------+-------------+---------+------+
|  2 | Sistem1 | fdjgf       |      1 |                 1 |             1 |           1 | 0       | NULL |
|  6 | Sistem2 | koam        |      0 |                 3 |             1 |           0 | SADGS   | NULL |
+----+---------+-------------+--------+-------------------+---------------+-------------+---------+------+

Process_Systems

+----+-----------+----------+--------+---------+
| id | processId | systemId | active | remarks |
+----+-----------+----------+--------+---------+
|  4 |         4 |        2 |      1 | aa      |
|  8 |         7 |        2 |      1 | aa      |
| 11 |         9 |        2 |      1 | aa      |
| 15 |         4 |        6 |      0 | aa      |
+----+-----------+----------+--------+---------+

我有一个方法，processID是一个参数，必须以某种方式按该ID过滤所有Process_Systems，然后获取不属于Systems表的Process_Systems

Answer 1

一种方法是使用NOT IN subquery：

SELECT   *
FROM     Systems
WHERE    id NOT IN (
           SELECT systemid
           FROM   Process_Systems
           WHERE  processId = ?
         );

另一种方法是使用NOT EXISTS subquery：

SELECT   *
FROM     Systems
WHERE    NOT EXISTS (
           SELECT *
           FROM   Process_Systems
           WHERE  systemId = Systems.id
              AND processId = ?
         );

第三种方法是使用outer join：

SELECT   Systems.*
FROM     Systems LEFT JOIN Process_Systems ps
      ON ps.systemId = Systems.id
     AND ps.processId = ?
WHERE    ps.systemId IS NULL;

在sqlfiddle上查看。

有关各自性能差异的分析，请参阅@ Quassnoi的博客文章：

MySQL查询以获取不属于另一个表的所有项目

1 个答案: