mysql-从key/value表中加入基于2个键的表

哦,你想要:

  SELECT `object_id` 
    FROM `settings`  
   WHERE (`key` = 'A' AND `value`='foo') 
      OR (`key`= 'B' AND `value`='bar')
GROUP BY `object_id`
  HAVING COUNT(*) = 2

用途:

  SELECT `object_id` 
    FROM `settings`  
   WHERE `key` IN ('A', 'B')
GROUP BY `object_id`
  HAVING COUNT(DISTINCT `key`) = 2

或:

SELECT x.`object_id` 
  FROM `settings` AS x 
  JOIN `settings` AS y ON y.`object_id` = x.`object_id`  
 WHERE x.`key` = 'A' 
   AND y.`key` = 'B'