MYSQL returns empty result set? - mysql

Question

I have a table with the following structure:
CREATE TABLE IF NOT EXISTS `user_settings` (
`user_ID` smallint(6) unsigned NOT NULL,
`item` varchar(50) NOT NULL,
`value` text,
`app_ID` tinyint(4) NOT NULL DEFAULT '0',
KEY `user_ID` (`user_ID`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
# With these data
INSERT INTO `user_settings` (`user_ID`, `item`, `value`, `app_ID`) VALUES
(3, 'statusTrainer_ID', '0', 0),
(3, 'enabledApp', '1', 0),
(3, 'enabled_office_ID', '1', 1),
(3, 'enabled_office_ID', '2', 1),
(4, 'statusTrainer_ID', '1', 0),
(1, 'enabledApp', '1', 0),
(1, 'salesCode_ID_add', '1', 1),
(1, 'salesCode_ID_add', '2', 1),
(1, 'salesCode_ID_add', '3', 1),
(1, 'salesCode_ID_add', '20', 1),
(1, 'salesCode_ID_process', '2', 1),
(1, 'salesCode_ID_process', '3', 1),
(1, 'salesCode_ID_process', '20', 1);
I would like to run this query for data filtering
SELECT `user_ID`
FROM (`user_settings`)
WHERE (
`item` = 'enabledApp'
AND
`value` IN ('1')
)
AND
(
`item` = 'statusTrainer_ID'
AND
`value` IN ('0')
)
I am expecting '3' as result but MYSQL returns an empty set. why?? thanks for answer.
UPDATED
I solved it by subquery
SELECT distinct `user_ID`
FROM (`user_settings`)
WHERE user_ID IN(
SELECT `user_ID`
FROM (`user_settings`)
WHERE (
item = 'enabledApp'
AND
value IN (1)
))
AND user_ID IN(SELECT `user_ID`
FROM (`user_settings`)
WHERE (
item = 'statusTrainer_ID'
AND
value IN (0)
))
Demo
but it's little complicated...is there some cleaner solution????

Answer 1

You need an or:
SELECT `user_ID`
FROM (`user_settings`)
WHERE ( `item` = 'enabledApp' AND `value` IN ('1') ) OR
( `item` = 'statusTrainer_ID' AND `value` IN ('0') )
It returned the empty set because item cannot be both "enabledApp" and "statusTrainer_ID".
Oh, you are trying to get user ids that have both. Do it this way:
SELECT `user_ID`
FROM `user_settings`
GROUP BY `user_ID`
HAVING max(case when `item` = 'enabledApp' AND `value` IN ('1') then 1 else 0 end) = 1 and
max(case when `item` = 'statusTrainer_ID' AND `value` IN ('0') then 1 else 0 end) = 1
Demo