Question

Two temp tables are created and then loaded…Here’s the schema.

Create table #SH ([date] datetime,
        sched_id int,
        agent_id int)

Create table #SD (sched_id int,
        start_minute int,
        length int,
        exception_code int)

(Schema and design is something I can’t change unfortunately, both temp tables are loaded from flat files. I can introduce and load new temp tables if needed).

A little background – The #SH header table holds a persons schedule as ‘Start_minute’ and goes for ‘schedule_length’ in minutes. For example, if start minute and schedule length were both 480, that would read as 8am (8am = 480th minute) and goes until 4pm (480 minutes later, 4pm = 960th minute)

The #SD table holds exceptions to the header. In the example above, the person would likely have a lunch exception which would be start_minute = 720 and length of 30 (12:00 – 12:30).

Date and agent_id is the only thing I’m interested out of #SH, the exception info in #sd is what I’m interested in.

This query works:

Select [date],#sd.start_minute,#sd.length,#sd.start_minute + #sd.length as 'end_minute',agent_id
from #SH 
inner join #SD on #SD.sched_id = #sh.sched_id

*end_minute is ultimately a calculated value of start+length = end

This returns something like:

   Date     Start  length   end

1 2010-11-11 600    30  630

2 2010-11-11 630    40  670

3 2010-11-11 750    15  765

4 2010-11-11 800    40  840

Now I wish I could say this was over and walk away…but data entry issues exist. In line 1 and 2, the end time of line 1 lines up with the start time in line 2 and should be combined so my results look like this :

Date     Start  length     end

1 2010-11-11 600    70  670

2 2010-11-11 750    15  765

3 2010-11-11 800    40  840

Any idea’s on how to build this logic so I get the 3 lines back instead of 4? I’m working on joining the table to itself on #sd1.start + #sd1.length = #sd2.start for now.

And to further complicate…the example above was 2 lines that needed combined. I’ve come across a record that had 30 1 minute entries in succession that I will need to make into a single record. Fortunately they cannot overlap (you won’t have 2 records occupying the same minutes), but I don’t think the join statement I’m considering above will work for that.

Answer 1

No need for a CTE, all you need is a helper table. Create it once, like so:

Create Table DayMinute(Minute Integer)
Declare @M Integer
Set @M = 1
While (@M <= 24*60)
Begin
  Insert Into DayMinute(Minute) Values(@M)
  Set @M = @M + 1
End

Then, all you need is a bit of tricksiness:

Select 
  DM.Minute,
  SD.Sched_ID
Into #MinutesWithException
From 
  DayMinute As DM
  Inner Join #SD As SD
    On DM.Minute Between SD.Start_Minute And SD.Start_Minute + Length

Select
  MWE.Sched_ID,
  SH.[Date],
  SH.Agent_ID,
  [Start_Minute] = MWE.Minute,
  [End_Minute] = (Select Min(Last.Minute) -- First one to have no successor
                  From #MinutesWithException As Last
                  Where Last.Sched_ID = MWE.Sched_ID
                    And Last.Minute > MWE.Minute
                    And Not Exists(Select *
                                   From #MinutesWithException As Next
                                   Where Next.Sched_ID = MWE.Sched_iD
                                     And Next.Minute = Last.Minute + 1))
From 
  #MinutesWithException As MWE
  Inner Join #SH As SH
    On MWE.Sched_ID = SH.Sched_ID
Where
  Not Exists(Select * -- All those without predecessor
             From #MinutesWithException As Previous
             Where Previous.Sched_ID = MWE.Sched_ID
               And Previous.Minute = MWE.Minute - 1)

Remember, a lot of SQL problems can be solved by rephrasing them. Don’t ask “which ranges do not have a gap”, ask “which minutes have an interval”. The rest follows from there.