Question

我有一张表格如下：

DECLARE @tmp TABLE
    (
    userID int,
    testID int,
    someDate datetime
    )

在其中我存储日期以及两个ID值，例如

INSERT INTO @tmp (userID, testID, someDate) VALUES (1, 50, '2010-10-01')
INSERT INTO @tmp (userID, testID, someDate) VALUES (1, 50, '2010-11-01')
INSERT INTO @tmp (userID, testID, someDate) VALUES (1, 50, '2010-12-01')
INSERT INTO @tmp (userID, testID, someDate) VALUES (2, 20, '2010-10-01')
INSERT INTO @tmp (userID, testID, someDate) VALUES (2, 20, '2010-11-01')

我需要为每个userID / testID组合选择最新日期。所以，结果将是

userID  testID  someDate
1       50      2010-12-01
2       20      2010-11-01

这听起来很容易，但我无法弄清楚。 SQL Fiddle Here

Answer 1

SELECT userID, testID, MAX(someDate)
FROM @tmp
GROUP BY testId,userID;

fiddle

Answer 2

SELECT userId, testId, MAX(someDate)
FROM @tmp
GROUP BY testId, userId

http://www.sqlfiddle.com/#!6/d41d8/5205

Answer 3

尝试

SELECT t1.* FROM @tmp t1
INNER JOIN (SELECT userId, MAX(someDate) someDate
            FROM @tmp
            GROUP BY userId) t2
        ON t1.userId = t2.userId
       AND t1.someDate = t2.someDate

选择按ID分组的最新日期

3 个答案: