Use the Expression Editor to build SQL-like statements. Although you can enter an expression manually, use the point-and-click method. Select functions, ports, variables, and operators from the point-and-click interface to minimize errors when you build expressions. The maximum number of characters that you can include in an expression is 32,767.
You can evaluate expressions that you configure in the Expression Editor of an Expression transformation.
When you test an expression, you can enter sample data and then evaluate the expression. Evaluate expressions in reusable transformations in the Transformation Designer. Evaluate expressions in non-reusable transformations in the Mapping Designer. Some functions do not support evaluating an expression when you set the port data type to either Binary or Date/Time.