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 vote381 views1 answer
Sql how to get courses that i have made prerequisites
SQL
1 vote374 views1 answer
Sql select max value from multiple rows
SQL
5 votes364 views1 answer
Oracle create table comment
SQL
16 votes358 views2 answers
Add column to all tables after first column mysql
SQL
0 vote355 views1 answer
Mysql beautifier terminla
SQL
2 votes377 views5 answers
Eloquest how to select one specific column in database
SQL
4 votes435 views1 answer
Oracle table statistics
SQL
2 votes430 views1 answer
Find column in all stored procedures sql server
SQL
3 votes375 views2 answers
To_char sql
SQL
0 vote299 views1 answer
Oracle sql replace string in clob
SQL