using two check constraints in sql

Question

I am looking for a possibility to use two possibilities for one attribute. Here an example:

CREATE TABLE person (
 name VARCHAR(200), 
 age INTEGER CONSTRAINT adult 
 CHECK (age >= 18)
)

Here the code will call a Person adult if the age is over 18, but now I would like the to person is called child if he is under 18.

CREATE TABLE  Person (
Id INTEGER NOT NULL PRIMARY KEY,
power_level INTEGER NOT NULL,
evilness_level INTEGER NOT NULL,
name VARCHAR(256) NOT NULL UNIQUE,
)

or here if the person has an evilness_level of < 0 it's a super hero, otherwise it is a super villain.

have a good day!

Rahul Tripathi · Accepted Answer · 2016-01-13 07:19:31Z

1

You can try to create a TRIGGER like

CREATE TRIGGER trig_evilness_level_check BEFORE INSERT ON Person 
FOR EACH ROW 
BEGIN 
IF NEW.evilness_level < 0 THEN 
SET NEW.Name = 'super hero';
ELSE
SET NEW.Name = 'super villain';
END IF; 
END

Similarly you can create the Trigger for the age check also.

The reason why it is suggested to create a TRIGGER instead of a CHECK constraint is clear from the manual which says:

The CHECK clause is parsed but ignored by all storage engines.

answered Jan 13, 2016 at 7:19

Rahul Tripathi

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