Let's say I have the following column in my database:
Item:
id int PRIMARY KEY,
name string,
foreign_id FOREIGN KEY
Is there a way without querying the database before insertion each time, that one foreign key cannot contain two rows with the same name?
Sure, you want to add an (unique) index for your foreign key column. The SQL command to add that is
ALTER TABLE `mytable`
ADD UNIQUE INDEX `mytable_idx__1` (`foreign_id`);
If I understand correctly, you might want to use the UNIQUE constraint:
CREATE TABLE (
id INT PRIMARY KEY
, name VARCHAR(50) --or whatever you need
, foreign_id INT UNIQUE
FOREIGN KEY (foreign_id) REFERENCES...
);
As i Understand using FOREIGN KEY (foreign_id) REFERENCES --- will solve it. And make sure that the always make a unique key
of table as foreign key
for other table.
CREATE TABLE profile
(
id int NOT NULL PRIMARY KEY,
name varchar(50),
FOREIGN KEY (name)
REFERENCES member (name)
ON DELETE CASCADE
ON UPDATE CASCADE
) ENGINE=InnoDB ;
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.