Answers for "alter table add reference foreign key postgres"

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*/

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
);

postgres add foreign key alter table

CREATE TABLE orders (
    order_id SERIAL,
    dish_name TEXT,
    customer_id INTEGER REFERENCES customers (id)
);