Most efficient way to perform query - php

Question

My goal is to get all records from tables where foreign key values match with IDs returned by a subquery from another table.
I have tried several combinations of but they don't even compile.
To clarify, consider following query:
SELECT *
FROM `news`
WHERE IDFIRM IN (SELECT ID FROM firm WHERE Block=0)
AND Actual=1
This is a simple query, but besides the ID in this subquery, I need to also retrieve other columns and return them in response.
Something like this (but of course this doesn't work):
SELECT news.*, sub.name
FROM `news`,
(SELECT * FROM firm WHERE Block=0) AS sub
WHERE news.IDFIRM IN (SELECT sub.ID FROM sub)
AND news.Actual=1
I have an idea how to implement this using joins, but the problem is that there can be multiple IN statements (from different tables), like this:
SELECT *
FROM `news`
WHERE IDFIRM IN (SELECT ID FROM firm WHERE Block=0)
AND Actual=1
AND id_publisher IN (SELECT ID FROM publisher WHERE Block=0)
So this query can become quite different, depending on the request.
How can I create the most efficient query to solve this task? Or it is possible only with multiple queries?
Thanks.

Answer 1

You should definitely use JOIN instead of IN (SELECT ...):
Query 1:
SELECT *
FROM `news`
WHERE IDFIRM IN (SELECT ID FROM firm WHERE Block=0)
AND Actual=1
Replace this by:
SELECT news.*
FROM news
INNER JOIN form ON news.IDFIRM = form.ID
WHERE news.Actual=1
Query 2:
SELECT news.*, sub.name
FROM `news`,
(SELECT * FROM firm WHERE Block=0) AS sub
WHERE news.IDFIRM IN (SELECT sub.ID FROM sub)
AND news.Actual=1
Replace by:
SELECT news.*,
firm.name
FROM news
INNER JOIN firm ON news.IDFIRM = firm.ID
WHERE news.Actual=1
AND firm.Block=0
Query 3:
SELECT *
FROM `news`
WHERE IDFIRM IN (SELECT ID FROM firm WHERE Block=0)
AND Actual=1
AND id_publisher IN (SELECT ID FROM publisher WHERE Block=0)
Replace by:
SELECT news.*
FROM news
INNER JOIN firm ON news.IDFIRM = firm.ID
INNER JOIN publisher ON news.id_publisher = publisher.ID
WHERE news.Actual=1
AND firm.Block=0
AND publisher.Block=0
Adding tables and conditions
So the idea is that you add all the tables you need with clauses like this:
INNER JOIN table1 ON news.<foreign-key> = table1.ID
and that you add the conditions all in the WHEREclause, like this:
WHERE table1.field = <literal>
AND table2.field = <other literal>
AND ...

Answer 2

Assuming your your indexes are sane on both sides of the JOIN they will actually be leveraged, whereas subqueries might use one side.
SELECT [column_list]
FROM news n
INNER JOIN firm f
ON n.idfirm = f.id
INNER JOIN publisher p
ON n.idpublisher = p.id
WHERE n.actual = 1
AND f.block = 0
AND p.block = 0

Answer 3

You are already suggesting a JOIN.
You can use multiple JOIN's to get what you want.
SELECT * FROM news
JOIN firm ON IDFIRM = firm.ID
WHERE Block = 0
JOIN publisher ON id_publisher = publisher.ID
WHERE Block = 0
I'm doing this from memory but should get you close I think.