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 Clarity vs Speed Rate Topic Display Mode Topic Options
Which of these pieces of code would you use
a) Series of "If" statements
33.33%
2
b) The function call
16.67%
1
c) The select statement
50%
3
 Member Votes: 6, Anonymous Votes: 0. You don't have permission to vote within this poll.
Author
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 Posted Friday, October 26, 2007 11:58 AM
 Grasshopper Group: General Forum Members Last Login: Monday, October 29, 2012 11:24 AM Points: 22, Visits: 84
 The following all produce the same results. Which would you use in your production code and whya) a series of If statements if @gross_pay < 35.17 select @boo = 0 else if @gross_pay >= 35.17 and @gross_pay < 151 select @boo = 40 else if @gross_pay >= 151 and @gross_pay < 201 select @boo = 50 else if @gross_pay >= 201 and @gross_pay < 251 select @boo = 60 else if @gross_pay >= 251 and @gross_pay < 301 select @boo = 70 else if @gross_pay >= 301 and @gross_pay < 351 select @boo = 80 else if @gross_pay >= 351 select @boo = 90b) a function that calls the same series of if statements in "a)" SET @boo = dboMaxTempDeduction(@gross_pay)c) a Select statement SET @Boo = (SELECT 40 WHERE Exists(SELECT 1 WHERE @Inc > 32.5)) + isnull((SELECT ((convert(int, (@inc/50)) -3) * 10) + 10 WHERE EXISTS( SELECT 1 WHERE @inc > 150.01)),0) - isnull((SELECT ((convert(int, ((400.01 - @inc)/50)) -1) * -10) WHERE EXISTS( SELECT 1 WHERE @inc > 400)),0)The speed of execution for each of these in microseconds is is a) 4.86 b) 51.64 c) 8.26
Post #415562
 Posted Friday, October 26, 2007 12:51 PM
 SSCrazy Group: General Forum Members Last Login: Today @ 7:30 AM Points: 2,015, Visits: 22,625
 To be honest I wouldn't use any, instead I'd use a range table such as below, avoids hardwiring valuescreate table Ranges(GrossPayMin decimal(10,3) not null, GrossPayMax decimal(10,3) not null, Boo int not null, primary key(GrossPayMin,GrossPayMax))insert into Ranges(GrossPayMin,GrossPayMax,Boo) values(0, 35.17,0)insert into Ranges(GrossPayMin,GrossPayMax,Boo) values(35.17,151,40)insert into Ranges(GrossPayMin,GrossPayMax,Boo) values(151,201,50)...insert into Ranges(GrossPayMin,GrossPayMax,Boo) values(351,99999,90)select @Boo=Boofrom Rangeswhere @gross_pay>=GrossPayMinand @gross_pay
Post #415590
 Posted Friday, October 26, 2007 1:54 PM
 Grasshopper Group: General Forum Members Last Login: Monday, October 29, 2012 11:24 AM Points: 22, Visits: 84
 Agreed. This is another perfectly viable method. Putting it through the same Iteration test it comes out as the third slowest (23 microseconds per iteration). If having the data matrix dynamic is a requirement to the problem then it is the ONLY reasonable solution.
Post #415611
 Posted Friday, October 26, 2007 2:15 PM
 Right there with Babe Group: General Forum Members Last Login: Tuesday, May 17, 2016 11:36 AM Points: 756, Visits: 3,178
 Is it faster if a temp variable is used instead of a temp table?How about if the table was pre-created? The dynamic solutions are still hardcoding values, to be truly dynamic they would be in an existing lookup table and there wouldn't be any insert overhead.
Post #415617
 Posted Friday, October 26, 2007 2:44 PM
 SSCrazy Eights Group: Moderators Last Login: Monday, May 16, 2016 7:45 AM Points: 8,376, Visits: 780
 Actually I might do this personnallySET @boo = (CASE WHEN @gross_pay < 35.17 THEN 0WHEN @gross_pay < 151 THEN 40WHEN @gross_pay < 201 THEN 50WHEN @gross_pay < 251 THEN 60WHEN @gross_pay < 301 THEN 70WHEN @gross_pay < 351 THEN 80ELSE 90END)
Post #415626
 Posted Friday, October 26, 2007 2:50 PM
 SSCrazy Eights Group: Moderators Last Login: Monday, May 16, 2016 7:45 AM Points: 8,376, Visits: 780
 Sorry, it has both clarity and should have the speed you want.
Post #415627
 Posted Friday, October 26, 2007 3:29 PM
 Grasshopper Group: General Forum Members Last Login: Monday, October 29, 2012 11:24 AM Points: 22, Visits: 84
 I have tried the more dynamic lookup suggested earlier with both a fixed table and the table variable. Interestingly enough there is not a significant difference in the timing.For raw speed the verbose If statements wins over everything. The more convoluted select statement is next, followed by the Select then the function call.A side note: I was challenged to come up with my own version of the type of "Max" function that SQL lacks - the max between two variables - and this employs that methodology. There are few places one needs it but if you do this is as fast as it is ugly.
Post #415636
 Posted Friday, October 26, 2007 3:31 PM
 Grasshopper Group: General Forum Members Last Login: Monday, October 29, 2012 11:24 AM Points: 22, Visits: 84
 That is an excellent solution!
Post #415637
 Posted Friday, October 26, 2007 5:32 PM
 SSC-Forever Group: General Forum Members Last Login: Yesterday @ 10:03 PM Points: 42,077, Visits: 39,461
 Heh... no matter how you swing it, this whole thing is RBAR... if it's for a GUI single row proc... no problem... if it even comes near a batch, big problem. --Jeff Moden"RBAR is pronounced "ree-bar" and is a "Modenism" for "Row-By-Agonizing-Row".First step towards the paradigm shift of writing Set Based code: Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column." Helpful Links:How to post code problemsHow to post performance problems
Post #415656
 Posted Saturday, October 27, 2007 2:47 PM
 Grasshopper Group: General Forum Members Last Login: Monday, October 29, 2012 11:24 AM Points: 22, Visits: 84
 What you are saying is true. In the real world where this code was snatched from with a little bit of salty refactoring I avoided this process entirely. Goes back to an old axiom "If you don't like the answer - rethink the question." That is off subject though.I was very interested in where experienced, practical professionals would come down on the question of having to choose between "verbose maintainable and slow" vs "nicely black box but very slow" vs "efficient but not so obvious". I wanted to use some sample code that would demonstrate these notions. I fear I went afoul there. My apologies if I wasted anyones time.There are soapboxes everywhere but given a sort of "Sophies Choice" of code I wondered which side serious professionals would come down on. As a person who manages, trains or mentors people on a regular basis I keep trying to understand development choices others make as a part of training my thinking. For various reasons that responsibility brought me to where I had a need to visit the "clarity vs Speed" issue. Thank you to all of you who responded. Each and every response was very instructional.
Post #415743

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