如何获取一组的最新值

Question

我从下面给出的查询中得到 15 行，获得的值也显示在下图中

SELECT * FROM [SS_MatrixLearners] 
WHERE ssml_Id_learnercourse=7390 and ssml_id_matrix = 29 and ssml_Id_topic=47 
order by SSML_Id_LevelKey, SSML_Id_LevelValue

对于所有这些值，我还想要 SSML_CompletedByUserName 的单个值，它在 SSML_CompletionDate 列中具有最新日期。请帮助我如何获得该价值。仅供参考，我正在使用 c#

在 Web 表单中使用它

Answer 1

我想出了以下解决方案。

SELECT * into #temp FROM ( SELECT * FROM [SS_MatrixLearners] ORDER BY SSML_ID_LevelKey, SSML_Id_LevelValue) As rn FROM [SS_MatrixLearners] where ssml_Id_learnercourse = 7390 and ssml_id_matrix = 29 and ssml_Id_topic = 47) t WHERE rn = 1 Update #temp SET SSML_CompletedByUserName = (select top 1 ISNULL(SSML_CompletedByUserName,'') From [SS_MatrixLearners] WHERE ssml_Id_learnercourse=7390 and ssml_id_matrix = 29 and ssml_Id_topic=47 ORDER by SSML_CompletionDate desc ) SELECT * from #temp order by SSML_Id_LevelKey, SSML_Id_LevelValue DROP table #temp

如果能写一些优化查询就好了

如何获取一组的最新值

How to get the latest value for a group

c#

sql

nested-query