SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Turn negative numbers into 0


Turn negative numbers into 0

Author
Message
Chrissy321
Chrissy321
Ten Centuries
Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)Ten Centuries (1.3K reputation)

Group: General Forum Members
Points: 1254 Visits: 4715
Hello all,

I have a select statement something like this.

SELECT
....
COALESCE
(
here I take the first non-null from 4 conditions, the conditions are fairy complicated
) AS MyComplexCalc
FROM...

My additional requirement is that if the complicated calc returns a negative number replace that with 0.

The following should work but I don't like repeating the calc from a code maintenance or performance perspective. Is there something cleaner where I do not have to repeat the calc?



SELECT
....
CASE COALESCE (here I take the first non-null from 4 conditions, the conditions are fairy complicated) <0
THEN 0
ELSE
COALESCE
(
here I take the first non-null from 4 conditions, the conditions are fairy complicated
)
END AS MyComplexCalc
FROM...
The Dixie Flatline
The Dixie Flatline
SSCertifiable
SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)

Group: General Forum Members
Points: 5620 Visits: 6900
Use a cte, like so:


;with cte (newvalue) as (select COALESCE etc FROM sometable)

select case when newvalue < 0 then 0 else newvalue end as newvalue from cte



__________________________________________________

Against stupidity the gods themselves contend in vain. -- Friedrich Schiller
Stop, children, what's that sound? Everybody look what's going down. -- Stephen Stills
Paul White
Paul White
SSCoach
SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)

Group: General Forum Members
Points: 16326 Visits: 11355
You can avoid performing the complex calculation more than once:


DECLARE
@A INTEGER = NULL,
@B INTEGER = -351,
@C INTEGER = 45,
@D INTEGER = 999;

SELECT
Calculation.result * ((SIGN(Calculation.result) + 1) / 2)
FROM
(
SELECT TOP (1)
result = COALESCE(@A, @B, @C, @D)
ORDER BY result
) AS Calculation;





Paul White
SQLPerformance.com
SQLblog.com
@SQL_Kiwi
The Dixie Flatline
The Dixie Flatline
SSCertifiable
SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)SSCertifiable (5.6K reputation)

Group: General Forum Members
Points: 5620 Visits: 6900
And also...



-- To make result = 0 when @test < 0

declare @test int -7

select (ABS(@test)+@test)/2 as result




__________________________________________________

Against stupidity the gods themselves contend in vain. -- Friedrich Schiller
Stop, children, what's that sound? Everybody look what's going down. -- Stephen Stills
Paul White
Paul White
SSCoach
SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)

Group: General Forum Members
Points: 16326 Visits: 11355
CELKO (7/18/2011)
SIGN (1 + SIGN(x)) * x
but it means using x twice. Hide it in a CTE and use the twice.

CTEs generally don't help - the expression is evaluated twice.
I included the TOP trick as the only way I know to force the query processor to evaluate just once.



Paul White
SQLPerformance.com
SQLblog.com
@SQL_Kiwi
Paul White
Paul White
SSCoach
SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)SSCoach (16K reputation)

Group: General Forum Members
Points: 16326 Visits: 11355
The Dixie Flatline (7/18/2011)
And also...
select (ABS(@test)+@test)/2 as result


Neat!



Paul White
SQLPerformance.com
SQLblog.com
@SQL_Kiwi
mister.magoo
mister.magoo
SSCarpal Tunnel
SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)SSCarpal Tunnel (4.2K reputation)

Group: General Forum Members
Points: 4238 Visits: 7865
SQLkiwi (7/18/2011)

CTEs generally don't help - the expression is evaluated twice.
I included the TOP trick as the only way I know to force the query processor to evaluate just once.


Here is another way then (learned from Stefan G) to force the calculation to only happen once:



;with calc(result) as
(
select COALESCE(@A, @B, @C, @D)
union all
select null
from calc
where 1=0
)
select calc.result * ((sign(calc.result) + 1) / 2)
from calc



The recursive part of the CTE returns no extra data, but coerces sql into storing the results (it will plop the results in tempdb once there are enough I believe) rather than re-evaluating them - it's a nice little trick that can sometimes help.

MM


select geometry::STGeomFromWKB(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




  • Forum Etiquette: How to post Reporting Services problems
  • Forum Etiquette: How to post data/code on a forum to get the best help - by Jeff Moden
  • How to Post Performance Problems - by Gail Shaw

  • SQLRNNR
    SQLRNNR
    SSC-Dedicated
    SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)SSC-Dedicated (33K reputation)

    Group: General Forum Members
    Points: 33382 Visits: 18560
    SQLkiwi (7/18/2011)
    The Dixie Flatline (7/18/2011)
    And also...
    select (ABS(@test)+@test)/2 as result


    Neat!


    Agreed - good thinking there Bob



    Jason AKA CirqueDeSQLeil
    I have given a name to my pain...
    MCM SQL Server, MVP


    SQL RNNR

    Posting Performance Based Questions - Gail Shaw

    Go


    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

































































































































































    SQLServerCentral


    Search