Do query if a particular field has a NULL value

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Do query if a particular field has a NULL value

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PGG_CA
Starting Member

24 Posts

Posted - 2012-01-18 : 15:43:05

How do I do this?

If field1 has a null value
then do this query

It's the if statement that I'm having trouble writing.

Thanks.

ehorn
Master Smack Fu Yak Hacker

1632 Posts

Posted - 2012-01-18 : 15:47:47

How about something like the following structure:


IF NOT EXISTS (SELECT <field1> FROM <yourTable> WHERE <criteria equates to NOT null>)
BEGIN
	--do this query
END
ELSE
	--do something else

HTH.

PGG_CA
Starting Member

24 Posts

Posted - 2012-01-18 : 16:01:07

Thanks ehorn, but I need to explain further what I want to do.

In this particular record, if field1 is null
then I do this
else I do that

In the condition statement, if this "select field1 from table where PK=1)" returns null then ...

ehorn
Master Smack Fu Yak Hacker

1632 Posts

Posted - 2012-01-18 : 16:04:33

I see. What is the 'this' or 'that' you need to do? We can perform certain things inline using a case statement. Such as :


SELECT CASE WHEN field1 IS NULL THEN <some scalar value> ELSE <some other scalar value> END 
FROM <yourTable>

If we need to perform complex operations, we likely have to us seperate queries to perform such tasks. It really depends on the 'this' and 'that' that you require. :)

HTH.

PGG_CA
Starting Member

24 Posts

Posted - 2012-01-18 : 16:09:13

There's a very complicated update procedure to do when the condition statement returns a NULL. I don't want to modify the UPDATE, just want to insert this condition that if this particular field for this record is NULL then perform the update; otherwise, don't do anything.

ehorn
Master Smack Fu Yak Hacker

1632 Posts

Posted - 2012-01-18 : 16:11:04

Can you simply add the NULL condition to the UPDATE statement's WHERE criteria?

PGG_CA
Starting Member

24 Posts

Posted - 2012-01-18 : 16:48:25

I'd rather not.

X002548
Not Just a Number

15586 Posts

Posted - 2012-01-18 : 16:50:05

If it's very complicated..why don't you just do what ehorn said?

Brett

8-)

Hint: Want your questions answered fast? Follow the direction in this link
http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx

Want to help yourself?

http://msdn.microsoft.com/en-us/library/ms130214.aspx

http://weblogs.sqlteam.com/brettk/

http://brettkaiser.blogspot.com/

Lamprey
Master Smack Fu Yak Hacker

4614 Posts

Posted - 2012-01-18 : 17:27:36

quote:
Originally posted by PGG_CA

There's a very complicated update procedure to do when the condition statement returns a NULL. I don't want to modify the UPDATE, just want to insert this condition that if this particular field for this record is NULL then perform the update; otherwise, don't do anything.

From what you've said, it sounds like you will hit the DB multiple times when you only need to do it once. Assuming that is true, why would you want to perform unneeded DB operations and slow things down?

Perhaps, I don't understand what you are trying to achomplish. If I've not understood you correctly, please refer to these links to help clarify what you are trying to do:
http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx
http://www.sqlservercentral.com/articles/Best+Practices/61537/

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