SQL - Primary & Foreign Keys

Overview

Primary keys uniquely identify rows. Foreign keys enforce referential integrity across tables.

CREATE TABLE parents (
  id INT PRIMARY KEY,
  name VARCHAR(50) NOT NULL
);
CREATE TABLE children (
  id INT PRIMARY KEY,
  parent_id INT,
  FOREIGN KEY (parent_id) REFERENCES parents(id)
);

CREATE TABLE parents (
  id INT PRIMARY KEY,
  name NVARCHAR(50) NOT NULL
);
CREATE TABLE children (
  id INT PRIMARY KEY,
  parent_id INT REFERENCES parents(id)
);

CREATE TABLE parents (
  id INTEGER PRIMARY KEY,
  name TEXT NOT NULL
);
CREATE TABLE children (
  id INTEGER PRIMARY KEY,
  parent_id INTEGER,
  FOREIGN KEY (parent_id) REFERENCES parents(id)
);

Live Demo (SQLite)

id	seq	table	from	to	on_update	on_delete	match
0	0	tmp_p	parent_id	id	NO ACTION	NO ACTION	NONE

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