Question

我有一张像这样的表：

----------------------------------------
|uID|responseDate|field_01|field_02|etc|
+---+------------+--------+--------+---+
| 1 | 2011-12-02 |   yes  |    no  |   |
| 2 | 2011-11-25 |   no   |   yes  |   |
| 1 | 2012-01-02 |   no   |   yes  |   |
| 2 | 2012-12-01 |   no   |    no  |   |
| 3 | 2010-01-02 |   yes  |    no  |   |
+---+------------+--------+--------+---+

我想获得uID和responseDates，对field_01的最新回复为“是” - 所以我的查询应该返回：

------------------
|uID|responseDate|
+---+------------+
| 3 | 2010-01-02 |
+---+------------+

我正在使用内部联接，但不正确。这是我的疑问：

SELECT f.uID, f.responseDate
FROM form_05 as f
INNER JOIN (
    SELECT uID, max(responseDate) AS latest_date
    FROM form_05
    WHERE field_01 = 'yes'
    GROUP BY uID ) dmax
 ON dmax.uID = f.uID and dmax.latest_date = f.responseDate
 ORDER BY f.uID ASC;

然而，返回的是每个uID的最新条目，其中field_01为是，即：

------------------
|uID|responseDate|
+---+------------+
| 1 | 2011-12-02 | 
| 3 | 2010-01-02 |
+---+------------+

但我不希望如此。我想这样做只有每个uID的最新条目才有资格进行测试。我该如何重组查询？任何指针都非常感谢。

Answer 1

尝试一下，如果它不起作用，请告诉我：

select t2.uid, t2.responseDate from t2
left join (
    select t1.uid, max(t1.responseDate) as MaxDate from t1
    group by t1.uid
) as SubQuery on t2.uid = SubQuery.uid and t2.responseDate = SubQuery.MaxDate
where MaxDate is not null and field_01 = "yes"

MySQL：使用行的子集来检查where子句

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