How to do a IFNULL(count(*),0) in MySQL 5.5 - mysql

Question

I tried to do a IFNULL(count(),0) , or IF (count() > 0, count(*),0),
but it doesn't work, my row "counter" display "NULL" instead of 0 :/
Here is my query:
SELECT IF(fc.counter > 0, fc.counter, 0) counter, b.*, fc.* FROM client_branche cb INNER JOIN branche b On b.id = cb.branche_id LEFT OUTER JOIN (
SELECT count(*) as counter, ctn_b.branche_id as b_id
FROM `historique` h
INNER JOIN contenu_branche ctn_b ON ctn_b.contenu_id = h.contenu_id
INNER JOIN utilisateur u ON u.id = h.utilisateur_id
WHERE h.h_fini = 1 AND ( u.client_id = 1 OR u.client_id = 0 ) AND h.h_dateheure BETWEEN '2015-12-24' AND '2015-12-30'
group by ctn_b.`branche_id`)
fc ON fc.b_id = cb.branche_id WHERE cb.client_id = 1
So i tried to do that :
SELECT IF(fc.counter > 0, fc.counter, 0) counter, b.*, fc.* FROM client_branche cb INNER JOIN branche b On b.id = cb.branche_id LEFT OUTER JOIN (
SELECT IFNULL(count(*),0) as counter, ctn_b.branche_id as b_id
FROM `historique` h
INNER JOIN contenu_branche ctn_b ON ctn_b.contenu_id = h.contenu_id
INNER JOIN utilisateur u ON u.id = h.utilisateur_id
WHERE h.h_fini = 1 AND ( u.client_id = 1 OR u.client_id = 0 ) AND h.h_dateheure BETWEEN '2015-12-24' AND '2015-12-30'
group by ctn_b.`branche_id`)
fc ON fc.b_id = cb.branche_id WHERE cb.client_id = 1
Annnnd i failed. I hope someone will help me. Thanks a lot in advance, and sorry for my bad english, it's not my native language :)

Answer 1

The problem is probably that you have is multiple columns in the select have the same name -- counter. The best way to solve this is not to use * in the query, but to list the columns you want. Perhaps a simpler way is to rename the column:
SELECT (CASE WHEN fc.counter > 0 THEN fc.counter ELSE 0 END) as fc_counter,
b.*, fc.*
FROM client_branche cb INNER JOIN
branche b
On b.id = cb.branche_id LEFT OUTER JOIN
(SELECT count(*) as counter, ctn_b.branche_id as b_id
FROM `historique` h INNER JOIN
contenu_branche ctn_b
ON ctn_b.contenu_id = h.contenu_id INNER JOIN
utilisateur u
ON u.id = h.utilisateur_id
WHERE h.h_fini = 1 AND
u.client_id IN (0, 1) AND
h.h_dateheure BETWEEN '2015-12-24' AND '2015-12-30'
GROUP BY ctn_b.branche_id
) fc
ON fc.b_id = cb.branche_id
WHERE cb.client_id = 1;
I made a couple other small changes as well, such as using IN instead of OR and CASE (ANSI standard) instead of IF().
Note: If counter is never negative, the most colloquial way of writing the logic is COALESCE(counter, 0) rather than CASE or IF().

Answer 2

It will work. You are use counter alias in subquery and also main query. So try it
SELECT IF(fc.cou > 0, fc.cou, 0) counter, b., fc.FROM client_branche cb INNER JOIN branche b On b.id = cb.branche_id LEFT OUTER JOIN ( SELECT IFNULL(count(*),0) as cou, ctn_b.branche_id as b_id FROM historiqueh INNER JOIN contenu_branche ctn_b ON ctn_b.contenu_id = h.contenu_id INNER JOIN utilisateur u ON u.id = h.utilisateur_id WHERE h.h_fini = 1 AND ( u.client_id = 1 OR u.client_id = 0 ) AND h.h_dateheure BETWEEN '2015-12-24' AND '2015-12-30' group by ctn_b.branche_id) fc ON fc.b_id = cb.branche_id WHERE cb.client_id = 1

Answer 3

You need the IFNULL on the outer query (due to the LEFT JOIN), like so:
SELECT IF(IFNULL(fc.counter,0) > 0, IFNULL(fc.counter,0), 0) AS counter
, b.*, fc.*
FROM client_branche AS cb
INNER JOIN branche AS b ON b.id = cb.branche_id
LEFT JOIN (
SELECT count(*) AS counter, ctn_b.branche_id AS b_id
FROM `historique` AS h
INNER JOIN contenu_branche AS ctn_b ON ctn_b.contenu_id = h.contenu_id
INNER JOIN utilisateur AS u ON u.id = h.utilisateur_id
WHERE h.h_fini = 1 AND ( u.client_id = 1 OR u.client_id = 0 )
AND h.h_dateheure BETWEEN '2015-12-24' AND '2015-12-30'
GROUP BY ctn_b.`branche_id`
) AS fc ON fc.b_id = cb.branche_id
WHERE cb.client_id = 1
;
It is effectively a "no op" on the inner query, since count(*) there will never be null.