Question

我有这个问题：

SELECT *
FROM   (SELECT *
        FROM   EventLog AS el
               RIGHT JOIN (SELECT Min(id) AS gId
                           FROM   EventLog
                           WHERE  Value IS NOT NULL
                           GROUP  BY Value) AS e
                       ON el.Id = e.gId) AS el
       LEFT JOIN (SELECT userid           AS uId,
                         Max([timestamp]) AS ts
                  FROM   UserAdditionStamp
                  GROUP  BY UserId) AS ua
              ON el.UserId = ua.uId
WHERE  el.EventTypeId = 3

从中选择的示例数据是：

Id  UserId     ts                              TimeStamp
-----------------------------------------------
461  1         2014-11-17 10:01:27.443      2013-01-08 16:28:52.557
468  25        NULL                         2013-01-08 17:06:15.967
441  1         2014-11-17 10:01:27.443      2013-01-09 11:00:43.947
461  29        2013-01-05 16:28:52.557      2013-01-09 13:29:19.143

如何比较ts和TimeStamp日期？如何获得哪一个是最大日期？

主要想法是，如果ts小于TimeStamp，我应该在另一个表中插入数据。

Answer 1

SELECT *, CASE WHEN coalesce(timestamp,'01/01/1901')>coalesce(ts,'01/01/1901') THEN 1 ELSE 0 END TimeStampBigger
FROM   (SELECT *
        FROM   EventLog AS el
               RIGHT JOIN (SELECT Min(id) AS gId
                           FROM   EventLog
                           WHERE  Value IS NOT NULL
                           GROUP  BY Value) AS e
                       ON el.Id = e.gId) AS el
       LEFT JOIN (SELECT userid           AS uId,
                         Max([timestamp]) AS ts
                  FROM   UserAdditionStamp
                  GROUP  BY UserId) AS ua
              ON el.UserId = ua.uId
WHERE  el.EventTypeId = 3

TimeStamp和ts都可以作为外部select中的列名提供，因此可以进行比较。作为额外列中的输出（如上所述：TimeStampBigger）或where子句中的另一个条件。

比较select中的日期

1 个答案: