foreign keys postgres code example

Example 1: create table postgresql foreign key

CREATE TABLE so_items (
	so_id INTEGER,
  	...
	FOREIGN KEY (so_id) REFERENCES so_headers (id)
);

Example 2: sql foreign key

# A foreign key is essentially a reference to a primary
# key in another table.

# A Simple table of Users, 
CREATE TABLE users(
	userId INT NOT NULL,
  	username VARCHAR(64) NOT NULL,
  	passwd VARCHAR(32) NOT NULL,
  	PRIMARY KEY(userId);
);
# Lets add a LEGIT user!
INSERT INTO users VALUES(1000,"Terry","Teabagface$2");

# We will create an order table that holds a reference
# to an order made by our Terry
CREATE TABLE orders(
	orderId INT NOT NULL,
  	orderDescription VARCHAR(255),
  	ordererId INT NOT NULL,
  	PRIMARY KEY(orderId),
  	FOREIGN KEY (ordererId) REFERENCES users(userId)
);
# Now we can add an order from Terry
INSERT INTO orders VALUES(0001,"Goat p0rn Weekly",1000);

# Want to know more about the plight of Goats?
# See the link below

Example 3: 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;

Example 4: 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
);