Question

嗨我试着用情侣INNER JOIN做查询，我的错在哪里？

SELECT job_tbl.id，accounts.username AS starter，accounts.username AS worker，job_tbl.comment，job_tbl.date，job_tbl.status

FROM job_tbl

INNER JOIN帐户ON job_tbl.starter = accounts.id

INNER JOIN帐户ON job_tbl.worker = accounts.id

job_tbl table here：

+----+---------+--------+---------+------+--------+
| id | starter | worker | comment | date | status |
+----+---------+--------+---------+------+--------+
| 1  |    1    |    3   |   qwe   | date |   10   |
+----+---------+--------+---------+------+--------+
| 2  |    2    |    1   |   qwe   | date |   10   |
+----+---------+--------+---------+------+--------+

帐户表：

+----+------------+-----------+-------+
| id |  username  | extension | email |
+----+------------+-----------+-------+
| 1  |   Julia    |    100    | email |
+----+------------+-----------+-------+
| 2  |    Eve     |    101    | email |
+----+------------+-----------+-------+
| 3  |    Max     |    102    | email |
+----+------------+-----------+-------+

结果我希望它是：

+----+---------+--------+---------+------+--------+
| id | starter | worker | comment | date | status |
+----+---------+--------+---------+------+--------+
| 1  |  Julia  |   Max  |   qwe   | date |   10   |
+----+---------+--------+---------+------+--------+
| 2  |   Eve   |  Julia |   qwe   | date |   10   |
+----+---------+--------+---------+------+--------+

Answer 1

您没有指定将哪个accounts表实例用作启动器或工作器。试试这个：

SELECT job_tbl.id, job_tbl.description, Starter.username AS starter, Worker.username AS worker, job_tbl.comment, job_tbl.date, job_tbl.status
FROM job_tbl
INNER JOIN accounts AS Starter ON job_tbl.starter = Starter.id
INNER JOIN accounts AS Worker ON job_tbl.worker = Worker.id

Answer 2

问题是你要加入两个表而没有在表ALIAS上指定accounts导致模糊状态。

SELECT  a.*,
        b.username StarterName,
        c.userName WorkerName
FROM    job_tbl a
        INNER JOIN account b
            ON a.starter = b.id
        INNER JOIN account c
            ON a.worker = c.ID

要进一步了解联接，请访问以下链接：

Visual Representation of SQL Joins

MySQL，第二个INNER JOIN

2 个答案: