Question

Having a hard time with this seemingly VERY simple mysql query:

This does not work (valid, but returns no rows):

select * from events where type = 'Disposition' AND startDT > '2012-01-01'

All of the following queries DO work off the same data:

select * from events where type = 'Eval' AND startDT > '2012-01-01'    
-- (change the value to Eval it works!)

select * from events where type = 'Disposition' AND addedDT > '2012-01-01' 
-- (search a different date field it works!)

select * from events where type = 'Disposition'  
-- (get rid of the AND it works!)

select * from events where startDT > '2012-01-01'   
-- (again, no AND it works!)

I have tried variations on the bad query, that also do NOT work:

select * from events where `type` = 'Disposition' AND `startDT` > '2012-01-01'
select * from events where `type` = 'Disposition' AND `startDT` > '2012-01-01 00:00:00'
select events.* from events where `type` = 'Disposition' 
    AND `startDT` > '2012-01-01 00:00:00'

(also tried variations on the date, lower case disposition)

I did not have an index on these fields, so I added an index on startDT, then type+startDT (addedDT has one).
NO DIFFERENCE.

startDT and addedDT are DATETIME fields.
type is varchar 30

Any ideas?

—
If this helps, here is the explain output:

BAD ONE:

explain select * FROM `events` WHERE `startDT` > '2012-01-11 00:00:01' AND `type` = "Disposition" limit 1000
"id"    "select_type"   "table" "type"  "possible_keys" "key"   "key_len"   "ref"   "rows"  "Extra"
"1" "SIMPLE"    "events"    "range" "startDT,type"  "type"  "40"    NULL    "1" "Using where"

RIGHT SIDE:

explain select * FROM `events` WHERE `type` = "Disposition" limit 1000
"id"    "select_type"   "table" "type"  "possible_keys" "key"   "key_len"   "ref"   "rows"  "Extra"
"1" "SIMPLE"    "events"    "ref"   "type"  "type"  "32"    "const" "13760" "Using where"

LEFT SIDE:

explain select * FROM `events` WHERE `startDT` > '2012-01-11 00:00:01' limit 1000
"id"    "select_type"   "table" "type"  "possible_keys" "key"   "key_len"   "ref"   "rows"  "Extra"
"1" "SIMPLE"    "events"    "range" "startDT"   "startDT"   "8" NULL    "13760" "Using where"

SCHEMA:

CREATE TABLE `events` (
    `id` VARCHAR(80) NOT NULL,
    `pk` INT(11) NOT NULL AUTO_INCREMENT,
    `addedDT` DATETIME NOT NULL,
    `type` VARCHAR(30) NOT NULL,
    `startDT` DATETIME NOT NULL,
    PRIMARY KEY (`pk`),
    INDEX `addedDT` (`addedDT`),
    INDEX `startDT` (`startDT`),
    INDEX `type` (`type`, `startDT`)
)
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB
AUTO_INCREMENT=29407;

SAMPLE ROWS:

INSERT INTO `events` (`id`, `pk`, `addedDT`, `type`, `startDT`) VALUES ('FBF8CE96-AE86-36C6-3C27-E2AAD042476B', 29406, '2012-12-28 12:59:03', 'Disposition', '2012-12-28 12:59:00');
INSERT INTO `events` (`id`, `pk`, `addedDT`, `type`, `startDT`) VALUES ('12577DB6-9B22-FA73-89BD-E2A5C1764B6D', 29405, '2012-12-28 12:53:32', 'Disposition', '2012-12-28 12:53:00');

Answer 1

column startDT is of date type in your table, try comparing date as-

select * from events where `type` = 'Disposition' AND `startDT` > DATE('2012-01-01');