[英]how to create a foreign key where there are multipal primary key in another table
I have a table A in a database which have multiple primary keys - Primary key 1 and Primary key 2
. 我在数据库中有一个表A,它具有多个主键-
Primary key 1 and Primary key 2
。 Now I need the create a foreign key in another table having primary key 2 as foreign key 现在,我需要在另一个具有主键2作为外键的表中创建外键
CREATE TABLE ADMIN_INFO(
NAME VARCHAR(20),
EMAIL VARCHAR(20),
PHONE_NO VARCHAR(20),
POST VARCHAR(20),
USER_NAME VARCHAR(16) not null ,
PASSWORD VARCHAR(16),
G_NAME VARCHAR(20) not null,
PRIMARY KEY (user_name,g_name)
);
CREATE tablE Godam(
G_NO INT PRIMARY KEY AUTO_INCREMENT,
BILLNO VARCHAR(20),
MARK VARCHAR(20),
QTY INT,
REMARK VARCHAR(10),
G_NAME VARCHAR(20),
FOREIGN KEY(G_NAME) REFERENCES ADMIN_INFO(G_NAME)
);
You cannot do that, as G_NAME
column is not a primary key. 您不能这样做,因为
G_NAME
列不是主键。 You have created a composite key using two columns USER_NAME
and G_NAME
. 您已经使用两列
USER_NAME
和G_NAME
创建了组合键。 So you need to have both columns in your second table Godam
and create a foreign key using both the columns. 因此,您需要在第二个表
Godam
同时拥有这两个列,并使用这两个列创建外键。
CREATE TABLE Godam(
G_NO INT PRIMARY KEY AUTO_INCREMENT,
BILLNO VARCHAR(20),
MARK VARCHAR(20),
QTY INT,
REMARK VARCHAR(10),
USER_NAME VARCHAR(16) not null ,
G_NAME VARCHAR(20),
FOREIGN KEY(USER_NAME, G_NAME) REFERENCES ADMIN_INFO(user_name, G_NAME)
);
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