MySql 检查外键约束是否存在

Question

如果我有:

create table order_items
( 
  orderid int unsigned not null references orders(orderid),
  isbn char(13) not null,
  quantity tinyint unsigned,

  primary key (orderid, isbn)

);

如何检查 orderid int unsigned not null references orders(orderid) 外键是否存在？

Answer 1

您可以像这样使用 INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS:

SELECT *
FROM information_schema.REFERENTIAL_CONSTRAINTS
WHERE CONSTRAINT_SCHEMA = '<schema>'
AND REFERENCED_TABLE_NAME = 'order_items'
AND CONSTRAINT_NAME = 'orderid'