sql CHECK constraint not working properly

Question

I have created a table schedule with a check constraint:

mysql> create table schedule(order_date date, dely_date date
                             check(dely_date>order_date));
Query OK, 0 rows affected (0.50 sec)

When I insert a value which violates check constraint, sql reports no error.

 mysql> insert into schedule values('2015-11-20','2014-12-25');
Query OK, 1 row affected (0.10 sec)

mysql> select * from schedule;
+------------+------------+
| order_date | dely_date  |
+------------+------------+
| 2015-11-20 | 2014-12-25 |
+------------+------------+
1 row in set (0.00 sec)

I have inserted a dely_date which comes before order_date.

score 2 · Answer 1 · answered Dec 07 '15 at 11:39

2

Oh, it is working properly. According to the manual:

The CHECK clause is parsed but ignored by all storage engines

You may want to try a db that is a little more sane.

answered Dec 07 '15 at 11:39

Jakub Kania

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1

I like `sane` :) You should mention that one workaround is to use trigger. [Sane database example](https://data.stackexchange.com/stackoverflow/query/404686) + you need comman before `CHECK`. – Lukasz Szozda Dec 07 '15 at 11:42
what should i do so that sql reports error? – user3297764 Dec 07 '15 at 11:52
@lad2025: Good idea. You should consider writing an answer with it as I limited myself to mysql-bashing. – Jakub Kania Dec 07 '15 at 12:21
@user3297764 `CHECK` doesn't do anything at all in MySQL.Using a before insert trigger that lad2025 mentioned seems like a good way to implement the constraint you need. – Jakub Kania Dec 07 '15 at 12:22
1

@JakubKania Added answer – Lukasz Szozda Dec 07 '15 at 18:58

score 2 · Accepted Answer · edited May 23 '17 at 11:59

The CHECK constraint in MySQL is ignored as in Jakub Kania's answer

Example of working CHECK using SQL Server:

create table #schedule(order_date date,
dely_date date,
check(dely_date>order_date));

insert into #schedule values('2015-11-20','2014-12-25');
-- The INSERT statement conflicted with the CHECK constraint "CK_#schedule_A59B8DED". 
-- The conflict occurred in database "tempdb", table "dbo.#schedule___
-- __________________00000000C9D8". The statement has been terminated.

INSERT INTO #schedule values('2015-12-24','2015-12-25');

SELECT *
FROM #schedule;

LiveDemo

You can use trigger to do validation:

CREATE TABLE `schedule`(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
                        order_date DATETIME,
                        dely_date DATETIME);              

CREATE TRIGGER `schedule_trg_ins` BEFORE INSERT ON `schedule`
FOR EACH ROW
BEGIN
    IF NOT(New.dely_date>New.order_date) THEN
    SIGNAL SQLSTATE '10000'
        SET MESSAGE_TEXT = 'check constraint on schedule failed during insert';
    END IF;
END;

CREATE TRIGGER `schedule_trg_upd` BEFORE UPDATE ON `schedule`
FOR EACH ROW
BEGIN
    IF NOT(New.dely_date>New.order_date) THEN
    SIGNAL SQLSTATE '10000'
        SET MESSAGE_TEXT = 'check constraint on schedule failed during update';
    END IF;
END;

INSERT INTO `schedule`(order_date, dely_date)
VALUES ('2015-12-24','2015-12-25');

INSERT INTO `schedule`(order_date, dely_date)
VALUES ('2015-12-26','2015-12-25');
-- check constraint on schedule failed during insert

UPDATE `schedule`
SET order_date = '2015-12-26'
WHERE id = 1;
-- check constraint on schedule failed during update

SqlFiddleDemo

@user3297764 Because MySQL does not implement `CHECK` syntax. It is only placeholder. — Lukasz Szozda, Dec 08 '15 at 06:54

sql CHECK constraint not working properly

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