Question

样本数据表：

eventDate           eventText
------------------- ----------
2018-05-01 12:00:00 Some event
2018-05-02 13:00:00 Some event
2018-05-03 11:00:00 Some event
2018-05-04 11:00:00 Some event
2018-05-05 15:00:00 Some event
2018-05-06 14:00:00 Some event
2018-05-07 17:00:00 Some event
2018-05-08 16:00:00 Some event
2018-05-09 12:00:00 Some event
2018-05-10 11:00:00 Some event

我希望在特定日期之后检索所有记录，但ALSO在该日期之前记录达到特定最大记录数。

例如，假设我要求2018-05-05或之后的所有记录。

SELECT * FROM myTable WHERE eventDate >= '2018-05-05' ORDER BY eventDate

eventDate           eventText
------------------- ----------
2018-05-05 15:00:00 Some event
2018-05-06 14:00:00 Some event
2018-05-07 17:00:00 Some event
2018-05-08 16:00:00 Some event
2018-05-09 12:00:00 Some event
2018-05-10 11:00:00 Some event

但是现在我想在同一个查询结果中包含，最多两个记录在2018-05-05之前。所以：

SELECT * FROM myTable WHERE eventDate >= '2018-05-05' ORDER BY eventDate -- pseudocode "AND OR eventDate < 2018-05-05 WITH MAXIMUM EXTRA RECORDS 2 eventDate eventText ------------------- ---------- 2018-05-03 11:00:00 Some event 2018-05-04 11:00:00 Some event 2018-05-05 15:00:00 Some event 2018-05-06 14:00:00 Some event 2018-05-07 17:00:00 Some event 2018-05-08 16:00:00 Some event 2018-05-09 12:00:00 Some event 2018-05-10 11:00:00 Some event

最大记录是最大记录，因此如果没有足够的条目可以且不应该是错误：

SELECT * FROM myTable WHERE eventDate >= '2018-05-02' ORDER BY eventDate -- pseudocode "AND OR eventDate < 2018-05-02 WITH MAXIMUM EXTRA RECORDS 10 eventDate eventText ------------------- ---------- 2018-05-01 12:00:00 Some event 2018-05-02 13:00:00 Some event 2018-05-03 11:00:00 Some event 2018-05-04 11:00:00 Some event 2018-05-05 15:00:00 Some event 2018-05-06 14:00:00 Some event 2018-05-07 17:00:00 Some event 2018-05-08 16:00:00 Some event 2018-05-09 12:00:00 Some event 2018-05-10 11:00:00 Some event

如果没有记录符合初始条件，我也希望它有效;在该实例中只返回两个记录：

SELECT * FROM myTable WHERE eventDate >= '2018-06-30' ORDER BY eventDate -- pseudocode "AND OR eventDate < 2018-06-30 WITH MAXIMUM EXTRA RECORDS 2 eventDate eventText ------------------- ---------- 2018-05-09 12:00:00 Some event 2018-05-10 11:00:00 Some event

我可以在一个查询中执行此操作吗？

如果可能的话，最好还是希望在没有存储过程或功能的情况下这样做。

用例是一个API，它将返回“所有当前和未来记录的列表，包括当前时间之前的最近两个先前记录”

Answer 1

你似乎想要：

SELECT t.*
FROM ((SELECT t.*
       FROM myTable t
       WHERE eventDate >= '2018-05-05'
       ORDER BY eventDate
      ) UNION ALL
      (SELECT TOP (2) t.*
       FROM myTable t
       WHERE eventDate < '2018-05-05'
       ORDER BY eventDate DESC
      )
     ) t
ORDER BY eventDate;

Answer 2

支票给戈登

但是可以更简单一些：

Microsoft.Extensions.DependencyInjection.MvcServiceCollectionExtensions.AddMvc

T-SQL在一个查询之后获取特定日期之后的所有记录以及固定数字？

2 个答案: