postgres add foreign key to existing table
ALTER TABLE tblA ADD COLUMN colA VARCHAR(10); /* 1st add column */
ALTER TABLE tblA ADD CONSTRAINT colA /* Make colA on tblA a foreign key */
FOREIGN KEY (colA) REFERENCES tblB (colB); /* colB must be a pk on tblB*/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;psql create table foreign keys
# id_user is the primary key of the table users:
create table lists(
id_list serial not null primary key,
id_user int references users(id_user),
is_temp int
);Copyright © 2021 Codeinu
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