T-SQL Fun

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T-SQL Fun

VM-723206

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September 15, 2009 at 8:08 pm

#204684

Comments posted to this topic are about the item T-SQL Fun

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SQLRNNR SSC Guru Points: 281334 More actions · Answer 1

This one made me pause for a sec - i was sure there was a trick somewhere in it (an extra space, some syntax or something). But straightforward it is.

Jason...AKA CirqueDeSQLeil
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dave.barter SSC Journeyman Points: 93 More actions · Answer 2

dave.barter

SSC Journeyman

Points: 93

September 16, 2009 at 1:16 am

#1054267

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dave.barter SSC Journeyman Points: 93 More actions · Answer 3

dave.barter

SSC Journeyman

Points: 93

September 16, 2009 at 1:21 am

#1054270

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Hafiz-1142834 SSC Veteran Points: 260 More actions · Answer 4

Can some one breif on the below comment in this context.

"This is one of the reasons to rely on checking 'equality' rather than 'inequality' "

Thanks

Joy Smith San SSC-Insane Points: 24877 More actions · Answer 5

I was not confused at all. I knew the answer is 'OK'.

But I dint understand the relevance of this question.

Hafiz-1142834 SSC Veteran Points: 260 More actions · Answer 6

Hafiz-1142834

SSC Veteran

Points: 260

September 16, 2009 at 2:58 am

#1054306

me too.

dave.farmer SSCrazy Points: 2431 More actions · Answer 7

At the risk of looking foolish, what am I missing here?

Is this not a case of:

if (condition) or (condition)

then

else

That's just an if-then-else statement.

Both conditions equate to false, so you get the else branch, that's how the logic always works... I don't see a gotcha, a sneaky trick, any specific knowledge at all here?

if (I am wrong)

then (tell me why)

else (agree with me)

RichB SSCrazy Eights Points: 9651 More actions · Answer 8

I guess its because people tend to evaluate 'true' things first, especially in IF clauses.

What we have here is a double negative, which requires more consideration and work through than

if @var = 'e' and @C = 'i'

then 'OK'

else 'Not ok'

which is much easier to evaluate as a human, and logically equivalent.

setiv Mr or Mrs. 500 Points: 536 More actions · Answer 9

declare @var char, @C char

set @C = 'I'

set @var = 'E'

if (ascii(@c) ascii('I')) OR (ascii(@var) ascii('E'))

begin

select 'not OK'

end

else

select 'OK'

WayneS SSC Guru Points: 95409 More actions · Answer 10

This is one of the reasons to rely on checking 'equality' rather than 'inequality'.

I have to agree with others. What does the above quote have to do with the question? Yes, the question does deal with two inequality matches, but it's straightforward and does as expected - what is it trying to teach that we should be using an equality match for?

Wayne
Microsoft Certified Master: SQL Server 2008
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rgillings SSCrazy Points: 2114 More actions · Answer 11

I am very confused as to why the comments stated:

"This is one of the reasons to rely on checking 'equality' rather than 'inequality'". The result was generated as expected.

Mauve SSChampion Points: 11316 More actions · Answer 12

This is one of the reasons to rely on checking 'equality' rather than 'inequality'.

Huh? This is just a simple compound condition test. The fact that it has an OR and "not equal to" comparison operators is immaterial.

In reality, for a certain business case, checking for equality could be totally wrong as you would have to check for every possible value vs. just checking the ones that are not allowed.

Perhaps it was meant to be coded as:

[font="Courier New"]IF (@c 'I') AND (@var 'E')[/font]

which is a common mistake when coding compound negative conditions.

[font="Arial Narrow"](PHB) I think we should build an SQL database. (Dilbert) What color do you want that database? (PHB) I think mauve has the most RAM.[/font]

Jesse McLain SSCommitted Points: 1782 More actions · Answer 13

I thought it was a decent question - the double negative almost made me answer 'NOT OK' rather than the correct answer, 'OK'. The author was simply pointing out that there is an issue with readability when using a double negative. You can disagree, but readability is about other people being able to read your code, not necessarily your own take on it.

Jesse McLain
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www.jessesql.blogspot.com

Michael Poppers SSCrazy Points: 2149 More actions · Answer 14

dave.farmer (9/16/2009)
At the risk of looking foolish, what am I missing here?
Is this not a case of:
if (condition) or (condition)
then
else
That's just an if-then-else statement.
Both conditions equate to false, so you get the else branch, that's how the logic always works... I don't see a gotcha, a sneaky trick, any specific knowledge at all here?
if (I am wrong)
then (tell me why)
else (agree with me)

agree with me 🙂