What is the Default Datatype of NULL?
NULL is undefined and every column can have NULL values
except columns with timestamp datatype (which represent NULL values
differently). There is a simple method to know the default datatype of NULL
values.
First, let us create a table with SELECT INTO TABLE Syntax
and then we will try to find out the datatype of the column where we have
stored NULL. Please note that we are not providing any datatype for the NULL
value.
SELECT NULL AS col
INTO #TempTable
Now let us look at the structure of the table and see what
datatype is assigned to the column named col in the table #TempTable
EXEC tempdb..sp_columns #TempTable
Now please look at the column named Type_Name in the
resultset. You will find that the default datatype is an Integer.
So, theoretically, I agree that it is difficult to come up
with the datatype of the NULL value, but in SQL Server the default datatype of
the NULL is an Integer.
