我有这 3 个表:
--company--
company_id (primary key)
name
--location--
location_id (primary key)
company_id (foreign key referencing company.company_id)
name
--asset--
asset_id (primary_key)
company_id (foreign key referencing company.company_id)
location_id (foreign key referencing location.location_id)
name
我想强制执行这一点:仅当 asset.company_id = location.company_id 时, Assets 的 location_id 才是可接受的
目前我正在通过应用程序强制执行此操作,我想知道是否可以仅使用 MySQL 来执行此操作。
最佳答案
drop table company;
create table company
( company_id int not null auto_increment,
name varchar(100) not null,
primary key(company_id)
)ENGINE=InnoDB
;
insert into company(name) values ('acme widgets');
insert into company(name) values ('goober chocolates');
insert into company(name) values ('Fat R Us');
drop table location;
create table location
( location_id int not null,
company_id int not null,
name varchar(100) not null,
primary key(company_id,location_id),
FOREIGN KEY (company_id ) REFERENCES company(company_id)
)ENGINE=InnoDB
;
insert into location(location_id,company_id,name) values (1,1,'Cambridge MA');
insert into location(location_id,company_id,name) values (1,2,'Boston MA');
insert into location(location_id,company_id,name) values (1,3,'Topeka KS');
insert into location(location_id,company_id,name) values (2,1,'Everywhere USA');
insert into location(location_id,company_id,name) values (2,666,'Fail Test this will fail');
create table asset
( asset_id int not null auto_increment,
company_id int not null,
location_id int not null,
name varchar(100) not null,
primary key(asset_id),
CONSTRAINT fk_asset_cl FOREIGN KEY (company_id,location_id)
REFERENCES location(company_id,location_id)
)ENGINE=InnoDB
;
insert into asset(company_id,location_id,name) values (1,1,'typewriter');
insert into asset(company_id,location_id,name) values (1,8,'typewriter fail');
请记住,在此示例中,您的 FK 必须返回到具有相同组合顺序(公司、位置)的键的单个父表
insert into asset(company_id,location_id,name) values (1,8,'typewriter fail');
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails ...
关于mysql - 仅当另一个外键匹配时才允许外键插入,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16641605/