Zoo tutorials:
[
SQL
|
CSS
|
Linux
|
Java
|
XML
]
Using:
SQL
zoo.net
Quick Ref.
SELECT
FUNCTIONS
SELECT
WHERE
SELECT
GROUP BY
SELECT
JOIN
SELECT
SELECT
INSERT
VALUES
INSERT
SELECT
UPDATE
DELETE
CREATE
TABLE
CREATE
VIEW
CREATE
INDEX
DROP
ALTER
TABLE
The SELECT ... LEFT JOIN statement
The LEFT JOIN will include rows from the left table even when the linking value is null.
games
yr
city
2004
Athens
2008
Beijing
2012
London
2032
null
city
name
country
Athens
Greece
Beijing
China
London
UK
Sydney
Australia
There is no data on where the 2032 games will be held.
The LEFT JOIN will include a row for 2032 even though it has no corresponding city.
SELECT games.yr, city.country FROM games LEFT JOIN city ON (games.city = city.name)
DROP TABLE games; DROP TABLE city;
CREATE TABLE city(name VARCHAR(20), country VARCHAR(20)); INSERT INTO city(name,country) VALUES ('Sydney','Australia'); INSERT INTO city(name,country) VALUES ('Athens','Greece'); INSERT INTO city(name,country) VALUES ('Beijing','China'); INSERT INTO city(name,country) VALUES ('London','UK'); CREATE TABLE games(yr INT, city VARCHAR(20)); INSERT INTO games(city,yr) VALUES ('Athens',2004); INSERT INTO games(city,yr) VALUES ('Beijing',2008); INSERT INTO games(city,yr) VALUES ('London',2012); INSERT INTO games(city,yr) VALUES (null,2032);
SELECT games.yr, city.country FROM games LEFT JOIN city ON (games.city = city.name)
Results
See also:
LEFT and RIGHT JOIN Tutorial
SELECT JOIN