Expression masking applies an expression to a port to change the data or create new data. When you configure expression masking, create an expression in the Expression Editor. Select input and output ports, functions, variables, and operators to build expressions.

You can concatenate data from multiple ports to create a value for another port. For example, you need to create a login name. The source has first name and last name columns. Mask the first and last name from lookup files. In the Data Masking transformation, create another port called Login. For the Login port, configure an expression to concatenate the first letter of the first name with the last name:

Select functions, ports, variables, and operators from the point-and-click interface to minimize errors when you build expressions.

The Expression Editor displays the output ports which are not configured for expression masking. You cannot use the output from an expression as input to another expression. If you manually add the output port name to the expression, you might get unexpected results.

When you create an expression, verify that the expression returns a value that matches the port datatype. The Data Masking transformation returns zero if the data type of the expression port is numeric and the data type of the expression is not the same. The Data Masking transformation returns null values if the data type of the expression port is a string and the data type of the expression is not the same.