Php 将一个表一列连接到另一个表多列

我试着搜索了很多例子，但是我的例子有点复杂，因为我有很多专栏。以下是一个简化版本：

使用者

类型

计算机

+------+--------+-------------------+------------------+--------------------+--------------------+
| pcid | typeid | bought_by_user_id | assigned_user_id | created_by_user_id | updated_by_user_id |
+------+--------+-------------------+------------------+--------------------+--------------------+
| 1    | 2      | 1                 | 3                | 1                  | 3                  |
+------+--------+-------------------+------------------+--------------------+--------------------+
| 2    | 1      | 2                 | 2                | 2                  | 2                  |
+------+--------+-------------------+------------------+--------------------+--------------------+
| 3    | 1      | 3                 | 2                | 3                  | 1                  |
+------+--------+-------------------+------------------+--------------------+--------------------+

我想要达到的结果是

+------+---------+----------------+---------------+-----------------+-----------------+
| pcid | type    | bought_by_user | assigned_user | created_by_user | updated_by_user |
+------+---------+----------------+---------------+-----------------+-----------------+
| 1    | Desktop | Tom            | Harry         | Tom             | Harry           |
+------+---------+----------------+---------------+-----------------+-----------------+
| 2    | Laptop  | Dick           | Dick          | Dick            | Dick            |
+------+---------+----------------+---------------+-----------------+-----------------+
| 3    | Desktop | Harry          | Dick          | Harry           | Tom             |
+------+---------+----------------+---------------+-----------------+-----------------+

我尝试过使用多个ONs，如下所示：

SELECT * FROM computers
LEFT JOIN types ON computers.typeid = types.typeid
LEFT JOIN users
ON users.userid = computers.bought_by_user_id
ON users.userid = computers.assigned_user_id
ON users.userid = computers.created_by_user_id
ON users.userid = computers.updated_by_user_id 

---

但那没用。。。Halp？

您需要对

用户

表进行多个连接：

SELECT 
    computers.pcid,
    types.typename,
    bought.username as bought_by_user,
    assigned.username as assigned_by_user,
    created.username as created_by_user,
    updated.username as updated_by_user
FROM computers
LEFT JOIN types ON computers.typeid = types.typeid
LEFT JOIN users bought ON computers.bought_by_user_id = bought.userid
LEFT JOIN users assigned ON computers.assigned_by_user_id = assigned.userid
LEFT JOIN users created ON computers.created_by_user_id = created.userid
LEFT JOIN users updated ON computers.updated_by_user_id = updated.userid

---

对于

computers

表中的四个用户列中的每一列，您都要对用户表进行单独的联接。每个联接表都有不同的别名，因此在select语句中，您可以访问联接表的任何列值。

您需要对

用户

表进行多个联接：

SELECT 
    computers.pcid,
    types.typename,
    bought.username as bought_by_user,
    assigned.username as assigned_by_user,
    created.username as created_by_user,
    updated.username as updated_by_user
FROM computers
LEFT JOIN types ON computers.typeid = types.typeid
LEFT JOIN users bought ON computers.bought_by_user_id = bought.userid
LEFT JOIN users assigned ON computers.assigned_by_user_id = assigned.userid
LEFT JOIN users created ON computers.created_by_user_id = created.userid
LEFT JOIN users updated ON computers.updated_by_user_id = updated.userid

---

对于

computers

表中的四个用户列中的每一列，您都要对用户表进行单独的联接。每个联接表都有不同的别名，因此在select语句中，您可以访问联接表的任何列值。

您需要对

用户

表进行多个联接：

SELECT 
    computers.pcid,
    types.typename,
    bought.username as bought_by_user,
    assigned.username as assigned_by_user,
    created.username as created_by_user,
    updated.username as updated_by_user
FROM computers
LEFT JOIN types ON computers.typeid = types.typeid
LEFT JOIN users bought ON computers.bought_by_user_id = bought.userid
LEFT JOIN users assigned ON computers.assigned_by_user_id = assigned.userid
LEFT JOIN users created ON computers.created_by_user_id = created.userid
LEFT JOIN users updated ON computers.updated_by_user_id = updated.userid

---

对于

computers

表中的四个用户列中的每一列，您都要对用户表进行单独的联接。每个联接表都有不同的别名，因此在select语句中，您可以访问联接表的任何列值。

您需要对

用户

表进行多个联接：

SELECT 
    computers.pcid,
    types.typename,
    bought.username as bought_by_user,
    assigned.username as assigned_by_user,
    created.username as created_by_user,
    updated.username as updated_by_user
FROM computers
LEFT JOIN types ON computers.typeid = types.typeid
LEFT JOIN users bought ON computers.bought_by_user_id = bought.userid
LEFT JOIN users assigned ON computers.assigned_by_user_id = assigned.userid
LEFT JOIN users created ON computers.created_by_user_id = created.userid
LEFT JOIN users updated ON computers.updated_by_user_id = updated.userid

---

对于

computers

表中的四个用户列中的每一列，您都要对用户表进行单独的联接。每个联接表都有一个不同的别名，因此在select语句中，您可以访问联接表的任何列值。

感谢您的回答，它成功了！所以给他们不同的别名是关键。谢谢你的回答，这很有效！所以给他们不同的别名是关键。谢谢你的回答，这很有效！所以给他们不同的别名是关键。谢谢你的回答，这很有效！所以给他们不同的别名是关键。