Alter table add foreign key mysql

Foreign key mySql

CREATE TABLE parent (
    id INT NOT NULL,
    PRIMARY KEY (id)
) ENGINE=INNODB;

CREATE TABLE child (
    id INT,
    parent_id INT,
    INDEX par_ind (parent_id),
    FOREIGN KEY (parent_id)
        REFERENCES parent(id)
        ON DELETE CASCADE
) ENGINE=INNODB;

Source: dev.mysql.com

Alter table add foreign key mysql

ALTER TABLE orders
ADD 
FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;

Drop foreign key

ALTER TABLE table_name
DROP CONSTRAINT fk_name;

Source: techonthenet.com

Alter table add column and foreign key mysql

ALTER TABLE database.table
  ADD COLUMN columnname INT DEFAULT(1),
  ADD FOREIGN KEY fk_name(fk_column) REFERENCES reftable(refcolumn) ON DELETE CASCADE;

Source: stackoverflow.com

Mysql alter add foreign key

ALTER TABLE ordenes ADD ticket VARCHAR(50) NOT NULL;
ALTER TABLE ordenes ADD CONSTRAINT fk_ticket FOREIGN KEY (ticket) REFERENCES tickets(ticket);

Source: es.stackoverflow.com

Add column mysql with foreign key

ALTER TABLE `TABLE_NAME`
ADD COLUMN `COLUMN_NAME` BIGINT(20) UNSIGNED NULL DEFAULT NULL AFTER `AFTER_COLUMN_NAME`, 
ADD FOREIGN KEY `FOREIGN_RELATION_NAME`(`COLUMN_NAME`) REFERENCES `FOREIGN_TABLE`(`FOREIGN_COLUMN`)  ON UPDATE SET NULL ON DELETE SET NULL

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