This tip was submitted to the SearchSQLServer.com tip library by member Parthasarathy Mandayam. Please let others know how useful it is via the rating scale at the end of the tip. Do you know a useful tip, timesaver or workaround? Submit it to our monthly tip contest and you could win a prize.
Adding null values to a variable can produce different results based on a SQL Server setting. Look at the statement, "Set concat_null_yields_null off" in the code below.
This tells SQL Server to ignore the null value and display the sum of the non-null variables as the result. Thus, the result in this example will be 'hello.'
If you change the code to use
set concat_null_yields_null on
Then the result will always be null since SQL Server will now no longer ignore the null variable and treat anything added to null as NULL.
Code: declare @var1 varchar(10) declare @var2 varchar(10) set concat_null_yields_null off set @var1='hello' set @var2=null print @var1+@var2
Do you have comments on this tip? Let us know.