Learning MySQL - FOREIGN KEY CONSTRAINTS
This tutorial covers what Foreign Keys are, what Constraints are, how to create foreign keys, constraints and how to implement actions based on the constraints.
MySQL Playlist:
MySQL Foreign Key Constraint Reference:
CODE SAMPLE:
ALTER TABLE characters DROP FOREIGN KEY `fk_character_race`;
DROP TABLE IF EXISTS races;
DROP TABLE IF EXISTS characters;
CREATE TABLE races (
race_id TINYINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
race_name VARCHAR(30) NOT NULL
)ENGINE=INNODB;
CREATE TABLE characters(
character_id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY Key,
character_name VARCHAR(50) NOT NULL,
race_id TINYINT UNSIGNED NOT NULL,
INDEX `idx_race`(race_id),
CONSTRAINT `fk_character_race`
FOREIGN KEY (race_id)
REFERENCES races(race_id) ON UPDATE CASCADE ON DELETE RESTRICT
)ENGINE=INNODB;
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