C# 连接表MySQL

我有多个表，并做了2个子选择（UserRecord、CustomerRecord），我想将它们合并到一个表中

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

我试过左，右，左外，右外。。。加入两张桌子，但我没有得到我想要的

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

您可以使用一个简单的

---

您想要的不是加入，而是联盟：

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

。。。它只是附加两个表中的记录

我要补充的是，订单不会是您在预期结果中显示的订单。如果顺序很重要，那么您应该从此联合中进行选择，并在此外部选择上添加一个明确的ORDERBY子句。比如：

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

---

如果表之间没有关系（如您的结果所示），我认为连接不是答案。尝试在从两个表中进行选择时使用并集，空作为不存在的列。使用（完整）

外部联接

。在mysql中，这可能意味着

UNION

a

RIGHT-OUTER-JOIN

与

LEFT-OUTER-JOIN

。作为参考，请参阅：Mysql Workbench不接受完全外部连接或仅接受外部连接谢谢，以前从未使用过用户联盟，但TrickWell i是否需要等待几分钟；）

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