Question

I have a SQL query which I want to optimize as its used as inner query of a SP.

 SELECT TOP 1 @CurrentStartDate = Strt_Dt FROM   (
 SELECT 1 AS seq, Stat, Strt_Dt, Est_Hrs_Comp, EndDate, Tckt_Id, Envr
  FROM   pipeline_rest_envr_info e
  WHERE  e.tckt_id = @TicketID AND stat = 'INPR'
  UNION
  SELECT TOP 1 2 AS seq, Stat, Strt_Dt, Est_Hrs_Comp, EndDate, Tckt_Id, Envr
  FROM   pipeline_rest_envr_info e
  WHERE  e.tckt_id = @TicketID AND stat = 'CMPL'
  ORDER BY enddate DESC
  UNION
  SELECT TOP 1 3 AS seq, Stat, Strt_Dt, Est_Hrs_Comp, EndDate, Tckt_Id, Envr
  FROM   pipeline_rest_envr_info e
  WHERE  e.tckt_id = @TicketID AND stat = 'PLND'
  ORDER BY strt_dt
  UNION 
  SELECT 4 AS seq, 'UNP', NULL, NULL, NULL, tckt_id, 'Unplanned'
  FROM   pipeline_rest_envr_info e
  WHERE  e.tckt_id = @TicketID
) aa
ORDER BY aa.seq

Is there any better way to use this query. I need this as I have lot logic having same type.

Answer 1

You are doing a union on 4 results from the same table for the same criteria, can you not just use a CASE statement? e.g.

SELECT 
    CASE Stat
         WHEN 'INPR' THEN 1
         WHEN 'CMPL' THEN 2
         WHEN 'PLND' THEN 3
         WHEN 'Unplanned' THEN 4
         ELSE 0 -- Not sure what your 'ELSE' case would be
    END as Seq,
    etc....
FROM   pipeline_rest_envr_info e 
WHERE  e.tckt_id = @TicketID 

You will still need case statements for all the fields which have logic, but it will include all data and will be a lot easier to read. Should also be a lot better for performance.