Question

您好我有一张表tbl_relations，看起来像

 -----------------------------------
 | id  |  source_id  |  target_id  |
 -----------------------------------
 | 2   |   2         |   4         |
 -----------------------------------
 | 3   |   5         |   7         | 
 -----------------------------------
 | 4   |   7         |   4         |
 -----------------------------------

其他表tbl_looksup看起来像

------------------------------
| id   |  language  |  value  |
------------------------------
| 1    |  1         |   abc   |
------------------------------
| 1    |  2         |   abc   |
------------------------------
| 2    |  1         |   abc   |
-------------------------------
| 2    |  2         |   abc   |
-------------------------------
| 5    |  1         |   abc   |
-------------------------------
| 5    |  2         |   abc   |
-------------------------------
| 7    |  1         |   abc   |
-------------------------------
| 7    |  1         |   abc   |
-------------------------------

tbl_relations以tbl_looksup和tbl_relations.source_id为tbl_relations.target_id

的方式映射到id of tbl_looksup

我的问题 我需要在tbl_relations source_id target_id中找不到tbl_looksup或id中的那些记录。这意味着tbl_looksup中不存在target_id = 4。更详细地说，tbl_relations的第一条记录tbl_looksup SELECT tbl_relations.source_id, tbl_relations.target_id, tbl_relations.id, tbl_looksup.`id` AS tblid FROM tbl_relations LEFT JOIN tbl_looksup ON tbl_relations.`source_id` != tbl_looksup.`id` OR tbl_relations.`target_id` != tbl_looksup.`id` GROUP BY tbl_relations.id中不存在{{1}}。这是错误的记录。我需要找出这些记录。

到目前为止我做了什么

{{1}}

Answer 1

为了获得所需的结果，您需要加入tbl_looksup两次，因为有两列依赖于该表。

SELECT  DISTINCT a.*
FROM    tbl_relations a
        LEFT JOIN tbl_looksup  b
            ON a.source_id  = b.id
        LEFT JOIN tbl_looksup  c
            ON a.target_id = c.id
WHERE   b.id IS NULL OR 
        c.id IS NULL

SQLFiddle Demo

要进一步了解联接，请访问以下链接：

Visual Representation of SQL Joins

输出

╔════╦═══════════╦═══════════╗
║ ID ║ SOURCE_ID ║ TARGET_ID ║
╠════╬═══════════╬═══════════╣
║  2 ║         2 ║         4 ║
║  4 ║         7 ║         4 ║
╚════╩═══════════╩═══════════╝

Answer 2

SELECT 
  tbl_relations.source_id,
  tbl_relations.target_id,
  tbl_relations.id 
FROM
  tbl_relations 
   WHERE tbl_relations.source_id not in (select id from tbl_looksup)
      OR tbl_relations.target_id not in (select id from tbl_looksup)

Answer 3

尝试添加此内容：

WHERE tbl_relations。target_id IS NULL

Answer 4

SELECT tbl_relations.id FROM tbl_relations 
  LEFT JOIN tbl_looksup 
    ON tbl_looksup.id = tbl_relations.source_id OR tbl_looksup.id = tbl_relations.target_id 
  WHERE tbl_looksup.id IS NULL

mysql连接一个表的两列

4 个答案: