When you use a null value in an expression containing a comparison operator, the

Data Integration Service

produces a null value. To check for null values in columns, you must use the ISNULL() in comparison expressions.

To return rows that do not contain null values, use the ISNULL function instead of the constant

!=

. For example, use

NOT ISNULL(Field_A)

.

The following expression results in a null value, and the Filter transformation does not return any rows:

Field_A!=NULL

.

You can also configure the Lookup transformation to treat null values as high or low in comparison operations. Use the Null Ordering property in the lookup source to configure how the

Data Integration Service

handles null values in comparison expressions in the Lookup transformation.