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 vote186 views1 answer
Except in sql
SQL
19 votes181 views3 answers
Grant mysql
SQL
0 vote235 views1 answer
Sql developer format sql
SQL
0 vote201 views2 answers
Suse stop MySQL
SQL
10 votes168 views4 answers
Primary key sql
SQL
0 vote167 views2 answers
Nosqlbooster query other collection
SQL
18 votes161 views3 answers
Mysql current date
SQL
3 votes172 views3 answers
How to set up an auto incrementing id db browser
SQL
10 votes170 views4 answers
Drop primary key
SQL
0 vote166 views1 answer
Sql query contains multiple ids
SQL