加入MySQL表

Question

我有多个表并做了2个子选择（UserRecord，CustomerRecord）我想合并到1个表中

UserRecord
========================
| RecordID | UserName |
========================
| 1        | Sara     |
| 1        | Tom      |
| 2        | Sara     |
| 2        | Kurt     |
| 3        | Fre      |
========================

Table: CustomerRecord
============================
| RecordID | CustomerName |
============================
| 1        | Jef          |
| 2        | Alex         |
| 2        | Peter        |
============================

Table: This should be the result
=======================================
| RecordID | UserName | CustomerName | 
=======================================
| 1        | Sara     | -            |
| 1        | Tom      | -            |
| 1        | -        | Jef          |
| 2        | Sara     | -            |
| 2        | Kurt     | -            |
| 2        | -        | Alex         |
| 2        | -        | Peter        |
| 3        | Fre      | -            |
=======================================

- = null

我尝试左，右，左外，右外...加入2张桌子，但我没有得到我想要的东西。

SELECT *
FROM UserRecord AS ur
INNER JOIN CustomerRecord AS cr ON ur.RecordID = cr.RecordID;

Answer 1

您可以使用简单的union

select recordid, username, null as customername from userrecord
union
select recordid, null, customername from customerrecord

Answer 2

你想要的不是连接，而是UNION：

SELECT RecordID, UserName, NULL AS CustomerName FROM UserRecord
UNION
SELECT RecordID, NULL AS UserName, CustomerName FROM CustomerRecord

...只是附加两个表中的记录。

我只是添加订单将不是您在预期结果中显示的订单。如果顺序很重要，那么您应该从此UNION中选择SELECT并在此外部选择上添加显式ORDER BY子句。类似的东西：

SELECT * FROM (
    SELECT RecordID, UserName, NULL AS CustomerName FROM UserRecord
    UNION
    SELECT RecordID, NULL AS UserName, CustomerName FROM CustomerRecord
) ORDER BY RecordID, UserName, CustomerName