Creating Constraints

Constraints, like expressions, enable you to filter or limit data based on criteria that you enter.

You can define a constraint or specify a reject link by both selecting an output link and clicking the Edit constraints button on the toolbar, or by double-clicking the output link header Constraint entry.

You can specify a constraint for each output link from a Transformer stage. You can also specify a particular link as a reject link. Reject links output rows that have not been written to any other output links from the Transformer stage.

In the example above, using the expression InsertFlag="Y" as a constraint verifies whether the lookup stages return a value. If no values were returned by the lookup stages, the InsertFlag field is set to N.