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Annoying NULLs Expand / Collapse
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Posted Monday, April 06, 2009 10:56 AM


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I checked this on 2005, and both answers marked as correct (A and D) work.

You have to run each SET/SELECT and then a SELECT @Val for each answer, with separate executions. I added a drop table #empty at the end as well.

The question has been edited to say "select all that apply"

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Post #691263
Posted Monday, April 06, 2009 3:11 PM
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Excellent QotD. Got it wrong which means I have learnt something .

Another little bit of the fun with Nulls learnt!
Post #691489
Posted Tuesday, April 07, 2009 9:18 AM
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I doubt if I can one day master the use of " NULL ". No matter how much I try to understand it, there always something left.
Well, " NULL " value handling is most of time are pain in the B**t.

very good QOD.


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Post #692163
Posted Monday, April 13, 2009 11:56 PM


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Create Table #Table
(
val int
)
Go

Select val From #Table
Go

Declare @val int
Select @val
Go

Declare @val int
Set @val = Null
Select @val
Go

Declare @val int
Select @val = Null From #Table
Select @val
Go

Declare @val int
Select @val = val From #Table
Select @val
Go

Declare @val int
Select @val = (Select val From #Table)
Select @val
Go

Drop Table #Table
Go

All the options mentioned in QoD returns NULL. So ideally speaking answer should contain all the options.

Mahesh


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Post #696316
Posted Tuesday, April 14, 2009 12:10 AM


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Don't forget to set the initial value of @val to -1 before each pass, you won't get the correct answers if you don't.

-d
Post #696319
Posted Thursday, April 16, 2009 5:19 AM
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I even tested for all the options and all came null, even adding the value to the variable.
Post #698299
Posted Thursday, April 16, 2009 6:37 AM


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harsha.bhagat1 (4/16/2009)
I even tested for all the options and all came null, even adding the value to the variable.

Check out the code that I posted last week and compare it to yours.



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Post #698346
Posted Friday, May 01, 2009 2:43 PM
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All the queries should return NULL.
Also I tested and the result it's the same.
Post #708778
Posted Friday, May 01, 2009 2:47 PM


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Mauricio Morales Soto (5/1/2009)
All the queries should return NULL.
Also I tested and the result it's the same.

You have to reset the variable to -1 before each test. See the code I posted earlier.



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Post #708780
Posted Wednesday, May 06, 2009 11:33 PM
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Hi All, I got null value for the below statement

set @val = null but for the below statement

select @val = (select val from #empty) i got

Invalid object name '#empty'

Is it i have to declare #empty first ?
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