Question

I have the following structure:

ID    CID    CAMPAIGN_ID   DATE(DATETIME)        DEVICE
1     123    88            2012-04-29 07:26:14   PC
2     123    88            2012-04-29 08:46:04   IPHONE
3     555    91            2012-04-29 08:36:04   IPAD

I’m trying to find a way to build a query that will return all the valid CIDs that first used the PC and then used the IPHONE (according to the date specified) under a specified campaign_id.

in the example above CID 123 falls into that category.

Answer 1

As @JohannBlais said in his comment, you need to join the table to itself on the desired criteria and then filter for your chosen campaign:

SELECT `t1`.`CID`
FROM
       `tbl` AS `t1`
  JOIN `tbl` AS `t2` ON (
        `t1`.`CID`            = `t2`.`CID`
    AND `t1`.`CAMPAIGN_ID`    = `t2`.`CAMPAIGN_ID`
    AND `t1`.`DATE(DATETIME)` < `t2`.`DATE(DATETIME)`
    AND `t1`.`DEVICE`         = 'PC'
    AND `t2`.`DEVICE`         = 'IPHONE'
)
WHERE `t1`.`CAMPAIGN_ID` = @specified_campaign;