MySQL GROUP BY trouble

[hobz]

I have 3 tables in a mysql database.
These tables together, form a QuickPoll structure, that looks like this:

table 1)
poll_base:
id, headline, date

table 2)
poll_option:
id, ref_base_id, text

table 3)
poll_voters:
ref_option_id, user_id

From these three tables, I would like to display:

Headline

Options (a WHILE loop with poll_options)

Number of votes on a poll_option (WHILE loop from poll_voters)

I order to obtain these outputs, I use the following MySQL query:

SELECT
	COUNT(voters.ref_option_id) AS votes,
	options.text AS options,
	options.id AS option_id
FROM
	hp_poll_option options,
	hp_poll_voters voters,
	hp_poll_base base
WHERE
	options.ref_base_id = base.id
AND
	options.id = voters.ref_option_id
AND
	WEEK(base.dato, 3) = WEEK(NOW(), 3)
GROUP BY
	options.id

The problem is this. If a poll_option has NO votes from poll_voters, this option does not SELECT (or display) in the query.

How can I change this?

[barand]

You need to use a 'left join'.

poll_option left join poll_voters

which will select all from options and nulls from voters if no match.

[hobz]

Thanks a bunch. Solved the problem in a jif!

Is there a difference between LEFT JOIN and JOIN?

[tomhath]

LEFT (OUTER) join means always return a row in the result set for the outer (or LEFT) table; if there is no matching row to join with on that table, substitute all NULL values for the columns that are selected from it.

An INNER join requires a match between all tables participating in the join in order to return a row in the results set.