left-join.md

http://sqlfiddle.com/#!9/b58cbd/1

This is a companion gist to the "Many explanations of JOIN are wrong, and people get confused" article.

Schema and initial data

CREATE TABLE t_a (
  id INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT
);
  
INSERT INTO t_a (id) VALUES (2), (3), (5);
  
CREATE TABLE t_b (
  id INTEGER NOT NULL PRIMARY KEY AUTO_INCREMENT
);
  
INSERT INTO t_b (id) VALUES (10), (20), (30), (40), (50);

Trivial match functions

SELECT t_a.id, t_b.id from t_a left join t_b on 1 = 1;

SELECT t_a.id, t_b.id from t_a left join t_b on 1 = 0;

etc.