Oracle - 在多个表中有外键
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Oracle - Having foreign keys in more than one table
提问by James Thompson
I'm not sure if one can do this but I need to have foreign key reference 2 tables.
我不确定是否可以做到这一点，但我需要有外键引用 2 个表。
Table1 has 2 columns (A PK, B)
Table2 has 2 columns (C PK, D)
Table3 has 3 columns (A PK, B PK, E) and is made up of the first two table.
表 3 有 3 列（A PK、B PK、E），由前两个表组成。
What I am hoping to do is something like the following:
我希望做的是如下所示：
create table Table3
(
A Varchar2 (4),
C Varchar2 (10),
E Char (1),
constraint PK_A_C primary key (A, C),
CONSTRAINT FK_A_C
FOREIGN KEY (A, C)
REFERENCES (Table1.A, Table2.B)
);
I hope that this makes some sort of sense.
我希望这有点道理。
Thanks
谢谢
James
詹姆士
回答by Bill Karwin
A given foreign key constraint describes a relationship from one child table to one parent table.
给定的外键约束描述了从一个子表到一个父表的关系。
You can, however, have two foreign key constraints, each pointing to the respective table:
但是，您可以有两个外键约束，每个都指向相应的表：
create table Table3
(
A Varchar2 (4),
C Varchar2 (10),
E Char (1),
constraint PK_A_C primary key (A, C),
CONSTRAINT FK_A
FOREIGN KEY (A)
REFERENCES Table1(A),
CONSTRAINT FK_B
FOREIGN KEY (C)
REFERENCES Table2(B)
);
回答by OMG Ponies
Use:
用：
CONSTRAINT fk_a FOREIGN KEY (a) REFERENCES TABLE1(a)
CONSTRAINT fk_b FOREIGN KEY (c) REFERENCES TABLE2(b)
Reference:
参考：
