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Which idea is better returning more than one result set or perform a join

Posted on 2008-10-07
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Last Modified: 2010-03-19
Which approach is better?

Returning Multiple Result sets:
SELECT [CAR_LOAD_ID]
      ,[CAR_ORDER_FL]
      ,[CAR_WELL_ID]
      ,[POSITION_NR]
      ,[EQUIP_AN]
      ,[COMMENT_DS]
  FROM [CAR_LOAD_T]
where CAR_ID = 2


select      [TRAIN_LOAD_ID]
      ,[TRAIN_ID]
      ,[TRAIN_TRACK_ID]
      ,[POSITION_ID]
      ,[DEST_TRAIN_CODE_ID]
      ,[LOAD_DT]
      ,[LOAD_BY_AN]
      ,[CAR_TRACK_ID]
      ,[WELL_ORDER_FL]
from [TRAIN_LOAD_T] tl
where CAR_ID = 2

select [CAR_LENGTH_NR]
from CARS_T
where CAR_ID = 2


or perform a join:

SELECT cl.[CAR_LOAD_ID]
      ,cl.[CAR_ORDER_FL]
      ,cl.[CAR_WELL_ID]
      ,cl.[POSITION_NR]
      ,cl.[EQUIP_AN]
      ,cl.[COMMENT_DS]
      ,tl.[TRAIN_LOAD_ID]
      ,tl.[TRAIN_ID]
      ,tl.[TRAIN_TRACK_ID]
      ,tl.[POSITION_ID]
      ,tl.[DEST_TRAIN_CODE_ID]
      ,tl.[LOAD_DT]
      ,tl.[LOAD_BY_AN]
      ,tl.[CAR_TRACK_ID]
      ,tl.[WELL_ORDER_FL]
,c.[CAR_LENGTH_NR]
  FROM [CAR_LOAD_T] cl
  join [TRAIN_LOAD_T] tl
on tl.[CAR_ID] = cl.[CAR_ID]
join CARS_T c
on c.CAR_ID = tl.CAR_ID
where c.CAR_ID = 2

I am using both in my app and i like the multiple result set approach. WAY less C# code to type cause a join returns the same data over and over and i have to check for different values.
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Question by:troycomp
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6 Comments
 
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Expert Comment

by:chapmandew
Comment Utility
It really depends.  If youre using the result sets separately, thene get them separately.  If you're using them together (a tran_id and a car_well_id at the same time) then join them.  Remember, don't pull back fields in the SELECT statement unless you absolutely need them.
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Author Comment

by:troycomp
Comment Utility
Im using them together. Whats so "bad" about the multiple result sets? If anything. A join returns more data than multiple result sets cause if a value is found once in table a but table b its found 10 times, you'll get table a results 10 times as well
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LVL 60

Expert Comment

by:chapmandew
Comment Utility
>>Whats so "bad" about the multiple result sets?
Nothing, really.  It all depends on how you want it.  If you're not going to need them combined, then don't combine them.
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Author Comment

by:troycomp
Comment Utility
Im working on a big project and its due at the end of this month. Im trying to write as little C# code as possible, but i want to make it as efficient as possible. So if im not gonna take a performance hit for not joining then i'm gonna use result sets. Will i take a performance hit for this?
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Accepted Solution

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chapmandew earned 250 total points
Comment Utility
Without knowing what you're dong in your app, there is no way I can tell you if your performance is going to be better or worse by choosing two queries or one.
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Author Comment

by:troycomp
Comment Utility
Thanks for your input
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