mysql - Order BY 根本不起作用

Question

从下表中，如何为每个 id、head 和 userId 选择最新的记录？这件事让我发疯。

"id"    "head"  "type"  "updated"   "userId"    "addedDate"
"1"     "2"     "0"     "1"         "1"         "2013-11-23 21:09:23"
"1"     "2"     "1"     "1"         "1"         "2013-11-23 21:09:40"
"2"     "2"     "0"     "1"         "1"         "2013-11-23 21:09:44"
"2"     "2"     "1"     "0"         "1"         "2013-11-23 21:09:47"

查询失败 - 都不会返回所需的结果

SELECT id, addedDate FROM test WHERE userId = 1 and head = 2 GROUP BY id HAVING MAX(addedDate);
SELECT id, addedDate FROM test WHERE userId = 1 and head = 2 GROUP BY id ORDER BY MAX(addedDate) DESC ;

当前错误结果

"id"    "addedDate"
"2"     "2013-11-23 21:09:44" // Incorrect. This is the first one for it
"1"     "2013-11-23 21:09:23" // Incorrect. This is the first one for it

期望的结果

"id"    "addedDate"
"2"     "2013-11-23 21:09:47" // The one that was added last
"1"     "2013-11-23 21:09:40" // The one that was added last 

编辑这里的整个问题是我不想在选择中使用 max() ，因为我正在使用 PDO::FETCH_KEY_PAIR

Answer 1

SELECT id, MAX(added_date) FROM test WHERE userId=1 AND head=2 Group By id