NULL

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NULL

Samith C

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August 14, 2012 at 8:44 pm

#262881

Comments posted to this topic are about the item NULL
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August 15, 2012 at 1:58 am

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Lokesh Vij SSChampion Points: 10836 More actions · Answer 1

An easy one! NULL means a value unknown or not defined yet, it may be equal to or may not be equal to 'Kannur'....Hence NULLS disappear from equality and inequality operations. They are handled separately 🙂

BTW...thanks for this refreshing question though!

~ Lokesh Vij

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rVadim Hall of Fame Points: 3969 More actions · Answer 2

Thank you for a nice easy question.

But I'm not sure about explanation (or maybe I'm just reading it wrong):

The Null value also matches the condition in case of Not Operators (<>,Not in ,Not like..) since it could possibly be a match.

I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

--Vadim R.

Lokesh Vij SSChampion Points: 10836 More actions · Answer 3

rVadim (8/14/2012)
I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.

+1

Yes that's correct!

~ Lokesh Vij

Guidelines for quicker answers on T-SQL question[/url]
Guidelines for answers on Performance questions

Link to my Blog Post --> www.SQLPathy.com[/url]

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Stuart Davies SSCoach Points: 19505 More actions · Answer 4

Easy question and point today - thanks

-------------------------------Posting Data Etiquette - Jeff Moden [/url]Smart way to ask a question
There are naive questions, tedious questions, ill-phrased questions, questions put after inadequate self-criticism. But every question is a cry to understand (the world). There is no such thing as a dumb question. ― Carl Sagan
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honza.mf SSCertifiable Points: 5519 More actions · Answer 5

Lokesh Vij (8/14/2012)
rVadim (8/14/2012)
I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.
+1
Yes that's correct!

+1

And even worse the answer is incorrect with ANSI NULLS off.

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SQL Surfer '66 SSCertifiable Points: 5161 More actions · Answer 6

SQL Surfer '66

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Points: 5161

August 15, 2012 at 2:53 am

#1525914

Interesting. Thanks for this one.

Gazareth One Orange Chip Points: 27737 More actions · Answer 7

honza.mf (8/15/2012)
Lokesh Vij (8/14/2012)
rVadim (8/14/2012)
I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.
+1
Yes that's correct!
+1
And even worse the answer is incorrect with ANSI NULLS off.

I did spend some time checking to see if there were any clues as to whether ANSI NULLS was on or off before I answered!

(Bob Brown) SSCrazy Points: 2705 More actions · Answer 8

Thanks for a nice easy question to celebrate the midweek.

Thomas Abraham SSChampion Points: 10761 More actions · Answer 9

Samith, thanks for contributing! Always interesting, and potentially contentious, when NULLs are brought up. But, good to keep thinking of them.

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sestell1 SSChampion Points: 10230 More actions · Answer 10

Nice question. This trips up a lot of people new to SQL and seems to lead to a lot of negative feelings towards NULL values.

(NULLs aren't bad, they're just often misunderstood!!)

mtassin SSC-Insane Points: 23099 More actions · Answer 11

sestell1 (8/15/2012)
Nice question. This trips up a lot of people new to SQL and seems to lead to a lot of negative feelings towards NULL values.
(NULLs aren't bad, they're just often misunderstood!!)

Totally agree. 🙂

I actually love NULLS, but then again I'm more familiar with them my devs are.

The sad thing are the number of tables with NULLable columns, but the apps explode when the data is actually NULL because the guys who made the database 10 years before I started didn't handle NULL correctly, or didn't make the column NOT NULL.

Ah one day we'll get them all cleaned up... 80 databases.... over 1500 tables used by nearly 50 applications.... probably not soon.

--Mark Tassin
MCITP - SQL Server DBA
Proud member of the Anti-RBAR alliance.
For help with Performance click this link[/url]
For tips on how to post your problems[/url]

mtassin SSC-Insane Points: 23099 More actions · Answer 12

honza.mf (8/15/2012)
Lokesh Vij (8/14/2012)
rVadim (8/14/2012)
I think any comparison against NULL will yield Unknown, which is not True, and therefore records won't be returned.
+1
Yes that's correct!
+1
And even worse the answer is incorrect with ANSI NULLS off.

At leats this thankfully won't be an issue sooner or later. SET ANSI NULLS OFF will throw an error in a coming SQL Release.

http://msdn.microsoft.com/en-us/library/ms188048.aspx

--Mark Tassin
MCITP - SQL Server DBA
Proud member of the Anti-RBAR alliance.
For help with Performance click this link[/url]
For tips on how to post your problems[/url]

SQLRNNR SSC Guru Points: 281334 More actions · Answer 13

EZPZ

Thanks

Jason...AKA CirqueDeSQLeil
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