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New Message on BDOTNET
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From: ClearableBarrel
Message 4 in Discussion
Hi
Prasanna,
good job done. :)
It was nice of you to have taken the initiative to post the
meeting discussion. I am sure it has helped a lot of other members like Pradeep.
keep it up....
Guys,
Prasanna was good enough to take this initiative when I
made a open call in the meeting for anybody to volunteer the writeup after our
vinod kumar shared the tip. As Pradeep many others who could not attend the
meeting would benefit from such posts. Prasanna I guess so, also feels good
abt helping the group! As Pooja mentioned, he also won a goodie for having taken
up this...just as a token of appreciation.
Good
Day
Rajiv
-----Original Message-----
From: Prasanna_kakanoor
[mailto:[EMAIL PROTECTED]
Sent: Monday, September 22, 2003
10:48 AM
To: [EMAIL PROTECTED]
Cc:
[EMAIL PROTECTED]
Subject: INFO : use of NULL in SQL
Server
New Message on BDOTNET
INFO :
use of NULL in SQL Server
Reply
Reply to Sender Recommend
Message 1 in
Discussion
From: Prasanna_kakanoor
Hi All,
Here is the tips discussed in the
last UG meeting.
In SQL SERVER, a value of NULL
indicates the value is unknown. A value of NULL is different
from an empty or zero value. No two null values are equal.
Comparisons between two null values, or between a NULL and any
other value, return unknown because the value of each NULL is
unknown.
Here is the tips to get the
records withour using any functions like ISNULL and the
IS NULL. My simple requirement
was to get all the vales in TableB that are not in
TableA.
I
have crated TabelA and TableB.
Table Strustutre.
TableA
ID
Name
1
Prasanna
2
Kashi
NULL
Raghu
TableB
ID
Name
Dept
1
Prasanna SW
2
Kashi SW
3
Raghu SQ
4 Sainath HR
5 Bala SQ
The first solution that came
to everyones mind was to use the following Query.
Select b.id from tableB b
Where b.id NOT IN (Select a.id from TableA
a)
GO
And that was a win for me to make them
understand what this really means. Since the presense of NULL
would make the query false for all the values and hence you will
get no. rows. To avoid this we mave a couple of options.
Starting from using ISNULL and the IS NULL expressions to
eliminate the NULL values. Or the best solution that I would
recommend is:
Select id from tableB b
Where
NOT Exists (Select 1 from TableA a Where a.id =
b.ID)
Go
Faster and more efficient ... This is
something we need to keep in mind while coding for our
applications. I also understand that if we were to SET
ANSI_NULLS OFF then also this behaviour is observed. But I
donot recommend that
approach.
Prasanna K
L<o:p></o:p>
Sr. Software
Engineer<o:p></o:p>
[MCAD(CM) |
MCSD.NET(Early
Achiever)]<o:p></o:p>
<o:p> </o:p> ZapApp India Private
Limited
Level G & 1, Explorer Building,
International TechPark, Whitefield Road,
Bangalore - 560 066. INDIA
91-80-
5115 6050 extn. 4061 (phone)
91-80- 841
1858 (fax)
[EMAIL PROTECTED]<o:p></o:p>
<o:p> </o:p>
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