Postgres 16

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CREATE TABLE colour (
  id SERIAL NOT NULL PRIMARY KEY,
  title TEXT NOT NULL,
  hex TEXT NOT NULL,
  rgb TEXT NOT NULL
);

CREATE TABLE


CREATE TABLE car (
  id TEXT NOT NULL PRIMARY KEY,
  colour_id INT NOT NULL REFERENCES colour(id)
);

CREATE TABLE


INSERT INTO colour(title, hex, rgb)
VALUES 
  ('red',   '#ff0000', '255, 0, 0'),
  ('blue',  '#00ff00', '0, 255, 0'),
  ('green', '#0000ff', '0, 0, 255');

INSERT 0 3


INSERT INTO car(id, colour_id)
VALUES 
  ('65d47b4d5b5db', 1),
  ('65d47b9402fef', 3);

INSERT 0 2


SELECT * FROM colour;


id
title
hex
rgb


1
red
#ff0000
255, 0, 0

2
blue
#00ff00
0, 255, 0

3
green
#0000ff
0, 0, 255



SELECT 3


SELECT * FROM car;


id
colour_id


65d47b4d5b5db
1

65d47b9402fef
3



SELECT 2


INSERT INTO car(id, colour_id)
VALUES 
  ('65d47f52032d5', 4);

ERROR:  insert or update on table "car" violates foreign key constraint "car_colour_id_fkey"
DETAIL:  Key (colour_id)=(4) is not present in table "colour".

id	title	hex	rgb
1	red	#ff0000	255, 0, 0
2	blue	#00ff00	0, 255, 0
3	green	#0000ff	0, 0, 255