如何筛选ROW_NUMBER（）

Question

我正在尝试从数据集中选择不同的NAME，但也返回其他列。我有它在某种程度上工作，但只是无法弄清楚如何把它结合在一起。

我怀疑我需要一个WITH x（或其他东西，但我不确定

这是CODE和它返回的数据的图像。从这里我只想表现出来 WHERE RN=1在图片中显示为红色圆圈

Select
    row_number() over (partition by tagname order by adddate) as RN,
    tagname,
    RIGHT(v_AlarmsWithTagname.TagName,charindex('.',REVERSE(v_AlarmsWithTagname.TagName))-1) as SCADA_tag, 
    convert(varchar(12) , adddate , 101) as AddDate,
    left(tagname,CHARINDEX('.',tagname)-1) as 'Table',
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid as 'Group',
    [CC_NOTE_LOG].dbo.SCADA_DB.dataset as 'Dataset', 
    [CC_NOTE_LOG].dbo.SCADA_DB.Description as 'Description'
FROM "Buckeye KB".dbo.v_AlarmsWithTagname
join 
    [CC_NOTE_LOG].dbo.SCADA_DB
on 
    RIGHT(v_AlarmsWithTagname.TagName,charindex('.',REVERSE(v_AlarmsWithTagname.TagName))-1)=[CC_NOTE_LOG].dbo.SCADA_DB.SCADA_SR_TAG
where
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid<>'test' and
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid not like 'Keep%' and
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid not like 'delete%' and
    Tagname not like '%.ES_%' and
    Tagname not like '%.OPC_%'

Answer 1

你只需要一个common table expression (CTE)。为此，您使用以下语法：;with CTE AS (query) SELECT whatever FROM CTE ...请查看下面的代码块。

;with CTE AS (
Select
    row_number() over (partition by tagname order by adddate) as RN,
    tagname,
    RIGHT(v_AlarmsWithTagname.TagName,charindex('.',REVERSE(v_AlarmsWithTagname.TagName))-1) as SCADA_tag, 
    convert(varchar(12) , adddate , 101) as AddDate,
    left(tagname,CHARINDEX('.',tagname)-1) as 'Table',
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid as 'Group',
    [CC_NOTE_LOG].dbo.SCADA_DB.dataset as 'Dataset', 
    [CC_NOTE_LOG].dbo.SCADA_DB.Description as 'Description'
FROM "Buckeye KB".dbo.v_AlarmsWithTagname
join 
    [CC_NOTE_LOG].dbo.SCADA_DB
on 
    RIGHT(v_AlarmsWithTagname.TagName,charindex('.',REVERSE(v_AlarmsWithTagname.TagName))-1)=[CC_NOTE_LOG].dbo.SCADA_DB.SCADA_SR_TAG
where
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid<>'test' and
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid not like 'Keep%' and
    [CC_NOTE_LOG].dbo.SCADA_DB.groupid not like 'delete%' and
    Tagname not like '%.ES_%' and
    Tagname not like '%.OPC_%'
)
SELECT * FROM CTE WHERE [RN] = 1

同样重要的是要注意，CTE不必直接跟随SELECT。有关CTE指南，请参阅以下链接：https://msdn.microsoft.com/en-us/library/ms175972.aspx