## Clarity vs Speed

Poll
 Which of these pieces of code would you use a) Series of "If" statements 33.33% 2 votes b) The function call 16.67% 1 vote c) The select statement 50% 3 votes Member votes: 6, Guest votes: 0. You don't have permission to vote in this poll
Author
Message
Paul G-468777
SSC Rookie

Group: General Forum Members
Points: 26 Visits: 84
The following all produce the same results. Which would you use in your production code and why
a) 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 = 90

b) 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
Mark Cowne
SSCrazy

Group: General Forum Members
Points: 2278 Visits: 23106
To be honest I wouldn't use any, instead I'd use a range table such as below, avoids hardwiring values

create 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=Boo
from Ranges
where @gross_pay>=GrossPayMin
and @gross_pay<GrossPayMax

____________________________________________________

Deja View - The strange feeling that somewhere, sometime you've optimised this query before

http://www.sqlservercentral.com/articles/Best+Practices/61537

Paul G-468777
SSC Rookie

Group: General Forum Members
Points: 26 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.
matt stockham
SSC Eights!

Group: General Forum Members
Points: 812 Visits: 3178
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.
Antares686
SSCrazy Eights

Group: Moderators
Points: 8704 Visits: 780
Actually I might do this personnally

SET @boo = (CASE
WHEN @gross_pay < 35.17 THEN 0
WHEN @gross_pay < 151 THEN 40
WHEN @gross_pay < 201 THEN 50
WHEN @gross_pay < 251 THEN 60
WHEN @gross_pay < 301 THEN 70
WHEN @gross_pay < 351 THEN 80
ELSE 90
END)

Antares686
SSCrazy Eights

Group: Moderators
Points: 8704 Visits: 780
Sorry, it has both clarity and should have the speed you want.

Paul G-468777
SSC Rookie

Group: General Forum Members
Points: 26 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.
Paul G-468777
SSC Rookie

Group: General Forum Members
Points: 26 Visits: 84
That is an excellent solution!
Jeff Moden
SSC Guru

Group: General Forum Members
Points: 52084 Visits: 40319
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.
Although they tell us that they want it real bad, our primary goal is to ensure that we dont actually give it to them that way.
Although change is inevitable, change for the better is not.
Just because you can do something in PowerShell, doesnt mean you should.

How to post code problems
How to post performance problems
Forum FAQs
Paul G-468777
SSC Rookie

Group: General Forum Members
Points: 26 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.

## Permissions

 You can't post new topics. You can't post topic replies. You can't post new polls. You can't post replies to polls. You can't edit your own topics. You can't delete your own topics. You can't edit other topics. You can't delete other topics. You can't edit your own posts. You can't edit other posts. You can't delete your own posts. You can't delete other posts. You can't post events. You can't edit your own events. You can't edit other events. You can't delete your own events. You can't delete other events. You can't send private messages. You can't send emails. You can read topics. You can't vote in polls. You can't upload attachments. You can download attachments. You can't post HTML code. You can't edit HTML code. You can't post IFCode. You can't post JavaScript. You can post emoticons. You can't post or upload images.

##### Select a forum
 SQL Server 2016      SQL Server 2016 - Administration      SQL Server 2016 - Development and T-SQL SQL Server 2014      Administration - SQL Server 2014      Development - SQL Server 2014 SQL Server 2012      SQL 2012 - General      SQL Server 2012 - T-SQL SQL Server vNext      SQL Server 14 - Administration      SQL Server 14 - Development SQL Server 2008      SQL Server 2008 - General      T-SQL (SS2K8)      June 2007 CTP      Working with Oracle      July CTP      SQL Server Newbies      Security (SS2K8)      SQL Server 2008 High Availability      SQL Server 2008 Administration      Data Corruption (SS2K8 / SS2K8 R2)      SQL Server 2008 Performance Tuning Cloud Computing      SQL Azure - Development      SQL Azure - Administration      Amazon AWS and other cloud vendors      General Cloud Computing Questions Reporting Services      Reporting Services      Reporting Services 2005 Administration      Reporting Services 2005 Development      Reporting Services 2008/R2 Administration      Reporting Services 2008 Development      SSRS 2012      SSRS 2014      SSRS 2016 Programming      Connecting      General      SMO/RMO/DMO      XML      Service Broker      Powershell      Testing      TFS/Data Dude/DBPro      SSDT      Continuous Integration, Deployment, and Delivery      R Services and R Language Data Warehousing      Integration Services      Strategies and Ideas      Analysis Services      Data Transformation Services (DTS)      Performance Point      Data Mining      PowerPivot      R language      Machine Learning Database Design      Disaster Recovery      Design Ideas and Questions      Relational Theory      Hardware      Virtualization SQLServerCentral.com      Anything that is NOT about SQL!      Contests!      Editorials      SQLServerCentral.com Announcements      SQLServerCentral.com Website Issues      Suggestions      Tag Issues with Content      Podcast Feedback      SQLServerCentral.com Test Forum      Articles Requested SQL Server 2005      Administering      Backups      Business Intelligence      CLR Integration and Programming.      Data Corruption      Development      Working with Oracle      SQL Server 2005 Compact Edition      SQL Server 2005 General Discussion      SQL Server 2005 Security      SQL Server 2005 Strategies      SS2K5 Replication      SQL Server Express      SQL Server 2005 Performance Tuning      SQL Server 2005 Integration Services      T-SQL (SS2K5)      SQL Server Newbies SQL Server 7,2000      Administration      Backups      Data Corruption      General      Globalization      In The Enterprise      Working with Oracle      Security      Strategies      SQL Server Newbies      Service Packs      SQL Server CE      Performance Tuning      Replication      Sarbanes-Oxley      T-SQL      SQL Server Agent SQL Server and other platforms      MySQL      Oracle      PostgreSQL      DB2      SQL Server and Sharepoint Older Versions of SQL (v6.5, v6.0, v4.2)      Older Versions of SQL (v6.5, v6.0, v4.2) Career      Certification      Employers and Employees      Events      Job Postings      Resumes and Job Hunters      Presentations and Speaking      Retired Members Testing Center      Question of the Day (QOD)      SQL Server Security Skills Microsoft Access      Microsoft Access Products and Books      Third Party Products         Extreme Technologies.         Innovartis         Embarcadero         SQL Sentry         Sonasoft         SQLCentric         Golden Gate Software         CA         Idera         Red Gate Software         Lumigent         Quest Software         ApexSQL      Discussions about Books         Discuss Programming Books          Discuss XML Books          Discuss T-SQL Books          Discuss Data Warehousing Books          Discuss SQL Server 2000 Books         Discuss DTS Books          Discuss SQL Server 7.0 Books Notification Services      Administration Article Discussions Future Versions      SQL 12