November 19, 2004 at 6:08 am
Hi Friends,
I m confused about whether to use IsNull() Function or wether I can simply use @variable IS Not NULL condition.But I am not sure that the condition such as
IF @variable IS NOT NULL
will work properly.
I want to know which one more efficient and correct
If ISNULL(@variable,0) <> 0
OR
IF @variable Is Not NULL
If anyone knows the difference between two please help me.
Regards
yuvraj
November 19, 2004 at 6:36 am
Generally use "is null" in a conditional.
Use isnull() to change the value from null to something else.
If null and 0 mean the same thing in your application, then isnull(@var, 0) can make conditionals simpler. But isnull(col, 0) would not use an index on col.
November 19, 2004 at 6:51 am
This might also be interesting:
http://qa.sqlservercentral.com/columnists/jtravis/understandingthedifferencebetweenisnull.asp
--
Frank Kalis
Microsoft SQL Server MVP
Webmaster: http://www.insidesql.org/blogs
My blog: http://www.insidesql.org/blogs/frankkalis/[/url]
November 19, 2004 at 9:39 am
The IS NULL in your example is more efficient and considered standard for this type of check. The reason is when you run
@var IS NULL
it evaluates true or false for the condition, but with
IsNull(@var,0) != 0
It must first check the condition for the sake of the function, replace the memory with the new value and then eavlauet the true or false of the != condition. So overall more cycles are consumed in the second situation.
In addition if 0 was ever allowed as a real value then your code would then fail to work properly in that case under the second condition.
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