Every movie needs a director and every rented movie needs to exist in the store. How do we make sure something in another table exists before inserting new data? This lesson will teach us about foreign keys and references.

CREATE TABLE directors (  id SERIAL PRIMARY KEY,  name VARCHAR(100) UNIQUE NOT NULL);CREATE TABLE movies (  id SERIAL PRIMARY KEY,  title VARCHAR(100) NOT NULL,  release_date DATE,  count_stars INTEGER,  director_id INTEGER REFERENCES directors(id));

Now, if we try to insert to movies table some new data which contains director_id is not inside directors table, it will report error

[PostgreSQL] Use Foreign Keys to Ensure Data Integrity in Postgres