Question

I have some problems to find a decission for an implementation.

I have to design a new database using mysql.
Now I found that I can do mysqlinternal actions on update or delete (NULL/NO ACTION / CASCADE).

EXAMPLE USING ON DELETE MYSQL INTERNAL:

CREATE  TABLE IF NOT EXISTS `mydb`.`users` (
  `idusers` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
  `name` CHAR(30) NOT NULL ,
  `mail` CHAR(50) NOT NULL ,
  PRIMARY KEY (`idusers`) )
ENGINE = InnoDB;


CREATE  TABLE IF NOT EXISTS `mydb`.`avatars` (
  `users_idusers` INT UNSIGNED NOT NULL ,
  `size` VARCHAR(45) NOT NULL ,
  `color` VARCHAR(45) NOT NULL ,
  `weight` VARCHAR(45) NOT NULL ,
  PRIMARY KEY (`users_idusers`) ,
  CONSTRAINT `fk_avatars_users`
    FOREIGN KEY (`users_idusers` )
    REFERENCES `mydb`.`users` (`idusers` )
    ON DELETE CASCADE
    ON UPDATE NO ACTION)
ENGINE = InnoDB;

Or is this way better and do each update delete completly from Application code:

CREATE  TABLE IF NOT EXISTS `mydb`.`users` (
  `idusers` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
  `name` CHAR(30) NOT NULL ,
  `mail` CHAR(50) NOT NULL ,
  PRIMARY KEY (`idusers`) )
ENGINE = InnoDB;



CREATE  TABLE IF NOT EXISTS `mydb`.`avatars` (
  `users_idusers` INT UNSIGNED NOT NULL ,
  `size` VARCHAR(45) NOT NULL ,
  `color` VARCHAR(45) NOT NULL ,
  `weight` VARCHAR(45) NOT NULL ,
  PRIMARY KEY (`users_idusers`) ,
  CONSTRAINT `fk_avatars_users`
    FOREIGN KEY (`users_idusers` )
    REFERENCES `mydb`.`users` (`idusers` ))
ENGINE = InnoDB;

Now, I’m not sure which is the best way which ensures a high performace level.

Should I implement relations in my programminglanguage and do a query on tables wich are relatet to my current dataset or should I implement the database in a way, which allows a mysql internal upate/delete Action

Thanks in advance.

Answer 1

My suggestion would be to implement the constraints in your RDBMS. It provides data integrity, better performance, less coding, and less chance of inconsistencies caused by the programmer.