我有三个表,每个表都有一个外键.当我执行连接时,我得到重复的列.

特定

mysql> describe Family;

+---------------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+---------------+-------------+------+-----+---------+-------+

| HEAD_name | varchar(45) | NO | PRI | | |

| Family_Size | int(11) | NO | | | |

| Gender | char(1) | NO | | | |

| ID_Number | int(11) | NO | | | |

| DOB | date | NO | | | |

| Supervisor_ID | int(11) | NO | MUL | | |

+---------------+-------------+------+-----+---------+-------+

6 rows in set (0.00 sec)

mysql> describe SUPERVISOR;

+-------------------+---------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-------------------+---------------+------+-----+---------+-------+

| Supervisor_ID | int(11) | NO | PRI | | |

| Supervisor_Name | varchar(45) | NO | | | |

| Supervisor_Number | decimal(10,0) | NO | | | |

| Center_ID | int(11) | NO | MUL | | |

+-------------------+---------------+------+-----+---------+-------+

4 rows in set (0.00 sec)

mysql> describe CENTER;

+-----------+-------------+------+-----+---------+-------+

| Field | Type | Null | Key | Default | Extra |

+-----------+-------------+------+-----+---------+-------+

| Center_ID | int(11) | NO | PRI | | |

| Location | varchar(45) | NO | | | |

+-----------+-------------+------+-----+---------+-------+

2 rows in set (0.00 sec)

我的查询声明：

SELECT * from Family

JOIN SUPERVISOR on ( Family.Supervisor_ID = SUPERVISOR.Supervisor_ID)

JOIN CENTER on (SUPERVISOR.Center_ID = CENTER.Center_ID);

我的目标是从连接中获取所有列的一行而不使用重复列.

那么我应该使用的SQL语句语法是什么？

解决方法:

默认情况下,如果使用*,MySQL将返回所有表的所有列.您需要在查询中明确输入列名称,以便按照您希望的方式检索它们.使用查询如下：

SELECT A.HEAD_name, A.Family_Size, A.Gender, A.ID_Number, A.DOB,

B.Supervisor_ID, B.Supervisor_Name, B.Supervisor_Number,

C.Center_ID, C.Location

FROM Family A

JOIN SUPERVISOR B on ( A.Supervisor_ID = B.Supervisor_ID)

JOIN CENTER C on (B.Center_ID = C.Center_ID);

标签：mysql,join,database,mysql-workbench

来源： https://codeday.me/bug/20191001/1837600.html