MySQL来自3个表的多个连接

我需要从资产A中选择所有记录。包括在这些记录中，我需要有链接到 来自资产的资产id，其中作者=scott@co.com或授权观众包括scott@co.com

我认为这接近我需要的，但它返回同一记录的多行：

SELECT
  A.*,
  C.lightbox_name,
  C.author,
  C.authorized_viewers
FROM
  media_tbl A
  LEFT JOIN lightbox_assets_tbl B ON A.asset_id = B.asset_id
  LEFT JOIN lightboxes_tbl C 
    ON B.lightbox_id = C.id
    AND C.author = "scott@co.com"
  LEFT JOIN lightboxes_tbl D ON D.authorized_viewers LIKE "scott@co.com"
ORDER BY A.id DESC

以下是表格：

lightboxes_tbl
+-----+----------------+---------------+---------------------+
|id   |lightbox_name   |author         |authoried_viewers    |
+-----+----------------+---------------+---------------------+
|100  | aircraft-types |scott@co.com   |jon@co.com,aj@co.com |
|101  | maintenance    |nicole@co.com  |jon@co.com           |
|102  | ramp           |nicole@co.com  |scott@co.com         |
+-----+----------------+---------------+---------------------+



lightbox_assets_tbl
+-----+-------------+-------------+---------------+----------+
|id   |lightbox_id  |asset_name   |asset_path     | asset_id |
+-----+-------------+-------------+---------------+----------+
|1    |100          |a321.jpg     |project1/imgs/ | 3700     |
|2    |100          |b757.jpg     |project1/imgs/ | 3444     |
|3    |101          |FlyBy.swf    |project4/imgs/ | 1444     |
|4    |102          |Door_757.swf |project5/imgs/ | 3701     |
+-----+-------------+-------------+---------------+----------+


assets_tbl
+-----+---------------------+-------------------------------------+
|asset_id   |asset_name           | asset_location                |
+-----------+---------------------+-------------------------------+
|3700       |a321.jpg             |Libraries\Library_Media\Images |
|200        |757_Taxi.swf         |Libraries\Library_Media\Images |
|3444       |b757.jpg             |Libraries\Library_Media\Images |
|1444       |FlyBy.swf            |Libraries\Library_Media\Images |
|3701       |Door_757.swf         |Libraries\Library_Media\Images |
+----------+---------------------+--------------------------------+

以下是查询的预期结果：

+-----------+---------------------+-------------------------------+------------------+-------------+------------------------+
|asset_id   |asset_name           | asset_location                |lightbox_name     | author      | authorized_viewers     |
+-----------+---------------------+-------------------------------+------------------+-------------+------------------------+
|3700       |a321.jpg             |Libraries\Library_Media\Images |aircraft-types    |scott@co.com |jon@co.com,aj@co.com    |
+-----------+---------------------+-------------------------------+------------------+-------------+------------------------+
|200        |757_Taxi.swf         |Libraries\Library_Media\Images |NULL              |NULL         |NULL                    |
+-----------+---------------------+-------------------------------+------------------+-------------+------------------------+
|3444       |b757.jpg             |Libraries\Library_Media\Images |aircraft-types    |scott@co.com |jon@co.com,aj@co.com    |
+-----------+---------------------+-------------------------------+------------------+-------------+------------------------+
|1444       |FlyBy.swf            |Libraries\Library_Media\Images |NULL              |NULL         |NULL                    |
+-----------+---------------------+-------------------------------+------------------+-------------+------------------------+
|3701       |Door_757.swf         |Libraries\Library_Media\Images |ramp              |nicole@co.com|scott@co.com            |
+----------+---------------------+--------------------------------+------------------+-------------+------------------------+

---

谢谢

我想知道为什么您需要两个灯箱表的连接。似乎第二次引用该表别名D是不必要的。看起来你可以用手术室

作为演示，复制查询中的谓词：

LEFT JOIN lightboxes_tbl C
       ON B.lightbox_id = C.id
      AND ( C.author = 'scott@co.com'
          OR C.authorized_viewers = 'scott@co.com'
          )

但如果授权用户包含逗号分隔的列表ACCKKK！！！，我怀疑您真的想在逗号分隔的列表中查找与项完全匹配的项。当前具有的LIKE比较相当于对authorized_Viewer列的全部内容进行equals比较。您可以添加“%”通配符来搜索作为字符串一部分的值

但这种方法也将匹配包含以下内容的字符串：。ebscott@co.com，这可能不是你真正想要的

您可以使用FIND_IN_SET函数在逗号分隔的列表中查找精确匹配项

LEFT JOIN lightboxes_tbl C
       ON B.lightbox_id = C.id
      AND ( C.author = 'scott@co.com'
          OR FIND_IN_SET('scott@co.com',C.authorized_viewers)
          )

存储逗号分隔的列表是一种SQL反模式。我推荐Bill Karwin的书：SQL反模式：避免数据库编程的陷阱

---

每条记录的多行似乎是由于D上的左连接造成的——该连接的on条件中没有任何内容将其与其他表相关联，从而导致笛卡尔积。这应该是加入lightbox_资产_tbl.lightbox_id，否？正确的DDL和/或SQLFIDLE会让您获得一个向上投票权。