Combining multiple CTE in TSQL

问题

I have two CTEs and I want to combine them together. I tried a lot but I got a syntax errors. First Part:

declare @TimeRanges as TABLE (SessionStart datetime, SessionEnd datetime);

     with TimeRanges as (
  select @Start as StartTime, @Start + @TimeRange as EndTime
  union all
  select StartTime + @TimeRange, EndTime + @TimeRange
    from TimeRanges
    where EndTime  < @Finish )

Here is the second part:

;with cte as
(
    select SessionStartTime as changetime,1 as CC from Calls
    union all
    select SessionCloseTime,-1 from Calls
)
    select top 1 changetime,rt from
    (
    select * from cte
        cross apply 
        (select SUM(cc) as rt from cte c where c.changetime<=cte.changetime) rt         
    ) v
    order by rt desc

What I want to do:

    @Start datetime, 
    @Finish datetime,
    @TimeRange time
AS
BEGIN

    SET NOCOUNT ON;
    declare @res int SET @res = 0

    declare @TimeRanges as TABLE (SessionStart datetime, SessionEnd datetime);

    with TimeRanges as 
     (  select @Start as StartTime, @Start + @TimeRange as EndTime
        union all  
        select StartTime + @TimeRange, EndTime + @TimeRange
        from TimeRanges
        where EndTime  < @Finish ),


    cte as
    (
    select SessionStart as changetime,1 as CC from TimeRanges
    union all
    select SessionEnd,-1 from TimeRanges
    )
    select top 1 changetime,rt from
    (
    select * from cte
        cross apply 
        (select SUM(cc) as rt from cte c where c.changetime<=cte.changetime) rt         
    ) v
    order by rt desc


    select StartTime, EndTime,cte.rt
    from TimeRanges as TR left outer join
      dbo.Test as Test on TR.StartTime <= Test.SessionStartTime 
      and Test.SessionCloseTime < TR.EndTime      
    where Test.ScenarioID = 24 
    group by TR.StartTime, TR.EndTime,cte.rt    
END

First CTE, groups or splits times according to the @timerange between StartTime and EndTime. For Example, StartTime 11:00 EndTime 11:10 and TimeRange 05:00(5 min) then splits them into two parts: 11:00 - 11:05 and 11:05 - 11:10. Second CTE counts something for each these ranges. Not important in here. I tried to combine them but I get there errors:

Invalid column name 'SessionStart'

Invalid object name 'TimeRanges'

回答1:

Because in the TimeRanges CTE, you've named the columns differently:

with TimeRanges as 
 (  select @Start as StartTime, @Start + @TimeRange as EndTime --StartTime and EndTime
    union all  
    select StartTime + @TimeRange, EndTime + @TimeRange
    from TimeRanges
    where EndTime  < @Finish ),


cte as
(
select StartTime as changetime,1 as CC from TimeRanges --StartTime, not SessionStart
union all
select EndTime,-1 from TimeRanges --EndTime
)
select top 1 changetime,rt from
(
select * from cte
    cross apply 
    (select SUM(cc) as rt from cte c where c.changetime<=cte.changetime) rt         
) v
order by rt desc

But you then attempt to refer to the CTE again in your second query. You can't do that - each CTE applies to a single query.

You could repeat it:

with TimeRanges as 
 (  select @Start as StartTime, @Start + @TimeRange as EndTime --StartTime and EndTime
    union all  
    select StartTime + @TimeRange, EndTime + @TimeRange
    from TimeRanges
    where EndTime  < @Finish )
select StartTime, EndTime,cte.rt
from TimeRanges as TR left outer join
  dbo.Test as Test on TR.StartTime <= Test.SessionStartTime 
  and Test.SessionCloseTime < TR.EndTime      
where Test.ScenarioID = 24 
group by TR.StartTime, TR.EndTime,cte.rt

来源：https://stackoverflow.com/questions/13134320/combining-multiple-cte-in-tsql

标签

tsql

common-table-expression