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

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

Update foreign key value in mysql

SET foreign_key_checks = 0;
UPDATE languages SET id='xyz' WHERE id='abc';
UPDATE categories_languages SET language_id='xyz' WHERE language_id='abc';
SET foreign_key_checks = 1;

Source: stackoverflow.com

Similar codes

0 vote348 views1 answer
Drop view sql
SQL
3 votes303 views1 answer
Sql is not like
SQL
0 vote307 views1 answer
Postgresql create query
SQL
7 votes293 views1 answer
Connect mysql docker
SQL
0 vote299 views1 answer
Sql convert float to string
SQL
-1 vote283 views1 answer
How to open blade file from blade in laravel
SQL
0 vote317 views2 answers
Dumping sql table
SQL
0 vote294 views1 answer
How to use select union and loop
SQL
1 vote310 views1 answer
Mysql return if it contains
SQL
0 vote317 views1 answer
Providername system.data. mysql
SQL