How to check whether GUID is null or empty?

Before going to look at this i suggest you to see GUID part 1 and part 2.

                                                         GUID part - 1

                                                         GUID part - 2

To check whether the given GUID is null, in SQL server, we have IS NULL keyword.

Declare @blog Uniqueidentifier

If(@blog IS NULL)
Begin
     Print 'The @blog Guid is null'
End
Else
Begin
     Print 'The @blog Guid is not null'

End


Where @blog is the variable. If we execute the above query obviously it prints 'The @blog Guid is null'

Now set the value to the variable @blog as follows.

Declare @blog Uniqueidentifier
set @blog=NEWID()
If(@blog IS NULL)
Begin
     Print 'The @blog Guid is null'
End
Else
Begin
     Print @blog

End


If we execute the above query obviously it prints the GUID value such as ' 17E2A682-F302-45BF-89E6-E46C0513D5D5' and if we you execute the query GUID value will be changed.

We can do the same thing as follows.

Declare @blog Uniqueidentifier

If(@blog IS NULL)
Begin
     set @blog=NEWID()
End


select @blog


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Have a look at the following query.

Declare @blog Uniqueidentifier

select ISNULL(@blog, NEWID())

In the above query we know that @blog is null then NEWID() will be returned and the result will be as '5A5AC20F-4D51-4A98-BF21-5AEB6FA05148'  and it will be changed if you reexecute.


If you execute the query by giving value to the variable as follows, then @blog variable result will be returned,

Declare @blog Uniqueidentifier
set @blog='5A5AC20F-4D51-4A98-BF21-5AEB6FA05148'

select ISNULL(@blog, NEWID())

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Empty GUID:

Generally empty GUID will be with all zero's as follows.

00000000-0000-0000-0000-000000000000

To get an empty GUID we need to use select statement as follows.

1) SELECT CAST(CAST(0 AS BINARY) AS UNIQUEIDENTIFIER)

2) SELECT CAST(0x0 AS UNIQUEIDENTIFIER)

We can use any one of the above. The following are the two scenarios to check the GUID is empty.

1) By comparing with empty.

Declare @blog UniqueIdentifier

Set @blog = '00000000-0000-0000-0000-000000000000'

If(@blog = '00000000-0000-0000-0000-000000000000')

Begin

     Print 'The @blog Guid is Empty'

End

Else

Begin

     Print 'The @blog Guid is not Empty'

End

In the above scenario the result is that 'The @blog Guid is Empty'

2) By using CAST 

Declare @blog UniqueIdentifier

Set @blog = '00000000-0000-0000-0000-000000000000'

If(@blog = Cast(0x0 as Uniqueidentifier))

Begin

     Print 'The @blog Guid is Empty'

End

Else

Begin

     Print 'The @blog Guid is not Empty'

End

In the above scenario the result is that 'The @blog Guid is Empty'