Monthly Archives: September 2014


Be aware when using ISNULL 1

ISNULL vs COALESCE in SQL Server

In our T-SQL programming, we mostly use ISNULL function to replace the null value of a column with another value. The same can be achieved using COALESCE function too. In this blog post, we are going to see a significant difference between NULL and COALESCE functions. We are going to discuss about the implicit conversion used by ISNULL and COALESCE functions.

What is COALESCE:

Evaluates the arguments in order and returns the current value of the first expression that initially does not evaluate to NULL.

Thus COALESCE gives a substitute value for NULL values from the given list of columns. It always returns the first NON-NULL from the list.

Syntax : – COALESCE ( expression [ ,…n ] )

COALESCE vs ISNULL

When we use ISNULL to get the substitute value for any NULL value it implicitly type casts the substitute as per the … More