Here is a very interesting question asked on the blog by Karthik. I really liked the question and I would like to discuss this here.
When Karthik was trying to run following query he was getting no result on the SSMS.
DECLARE @var1 numeric(10,2), @var2 numeric(10,2), @var3 numeric(10,2), @var4 numeric(10,2) SET @var1=12500 SET @var2=NULL SET @var3=500 SELECT @var4=(@var1+@var2+@var3) PRINT @var4
Here is the screenshot of the query executed. The reason behind no result was @var2 is assigned value to NULL. Later the same @var2 is added to another variables and finally assigned to @var4. Whenever NULL value is added to any other value the resultant values are NULL that leads to no result.
A NULL value can’t be printed using PRINT statement and that is the reason it does not print anything.
However, if you assign @var2 to any other value as displayed in following image – it will display the print value.
Alternatively, if you want to display the output of @var4 when @var2 is NULL, you can use SELECT instead of PRINT and you will be able to display the value of NULL.
I think this was very basic but very interesting question for sure and I like to write about it.
Reference: Pinal Dave (http://blog.sqlauthority.com)