Question

我正在尝试创建我认为是自我联接的东西，但是我无法获得它返回我想要的东西。我得到一个空集或一个关于非唯一表的错误

我试图简单地查询并仅返回“ To Tag”和“ From Tag”，但是我总是遇到非唯一表错误

    select a.from_tag as 'From Tag', b.to_tag as 'To Tag'  
    from termination_schedule a
    inner join termination_schedule b 
    on terminal_associations.term_assoc_id=b.from_id
    inner join termination_schedule a 
    on terminal_associations.term_assoc_id=a.from_id;

我要加入的两个表是：终端关联：

    +---------------+----------+----------------+----------+
    | term_assoc_id | tag      | terminal_strip | terminal |
    +---------------+----------+----------------+----------+
    |             1 | BC122EE1 | XP             | L1       |
    |             2 | BC122EE1 | XP             | L2       |
    |             3 | BC122EE1 | XP             | L3       |
    |             4 | BC122HS1 | 1              | L1-1     |
    |            10 | BC122HS1 | 1              | L1-2     |
    |             5 | BC122HS1 | 1              | L2-1     |
    |            11 | BC122HS1 | 1              | L2-2     |
    |             6 | BC122HS1 | 1              | L3-1     |
    |            12 | BC122HS1 | 1              | L3-2     |
    |             7 | BC122M1  | 1              | L1       |
    |             8 | BC122M1  | 1              | L2       |
    |             9 | BC122M1  | 1              | L3       |
    +---------------+----------+----------------+----------+

和终止时间表

| cable_no | from_id | to_id | core_mark |
+----------+---------+-------+-----------+
| 1001     |       1 |     4 | red       |
| 1001     |       2 |     5 | white     |
| 1001     |       3 |     6 | blue      |
| 1002     |      10 |     7 | red       |
| 1002     |      11 |     8 | white     |
| 1002     |      12 |     9 | blue      |
+----------+---------+-------+-----------+````

What I want to return is:
+----------+----------+-----------+----------+
| cable_no | From Tag | core_mark | To Tag   |
+----------+----------+-----------+----------+
| 1001     | BC122EE1 | red       | BC122HS1 |
| 1001     | BC122EE1 | white     | BC122HS1 |
| 1001     | BC122EE1 | blue      | BC122HS1 |
| 1002     | BC122HS1 | red       | BC122M1 |
| 1002     | BC122HS1 | white     | BC122M1 |
| 1002     | BC122HS1 | blue      | BC122M1 |
+----------+----------+-----------+----------+

Answer 1

这就是我的工作方式


select termination_schedule.cable_no, a.term_assoc_id as 'From Tag', termination_schedule.core_mark,b.term_assoc_id as 'To Tag'
FROM termination_schedule
LEFT JOIN terminal_associations a ON termination_schedule.from_id=a.term_assoc_id
LEFT JOIN terminal_associations b ON termination_schedule.to_id=b.term_assoc_id;````

MySQL自连接引用另一个表

1 个答案: