When you set a constraint, you enter an expression that evaluates to TRUE for each data row.

The Data Integration Service can read constraints from relational sources, logical data objects, physical data objects, or virtual tables. To set a constraint on a reusable physical data object, create a customized data object.

When the Data Integration Service reads constraints, it might drop the rows that do not evaluate to TRUE for the data rows based on the optimization method applied.

Before you set a constraint, you must verify that the source data satisfies the condition set by the constraint. For example, a source database has an AGE column that appears to have rows with AGE < 70. You can set a constraint with AGE < 70 on the source database. The Data Integration reads records from the source database with the constraint AGE < 70. If the Data Integration Service reads records with AGE >= 70, it might drop the rows with AGE >= 70.

In the database, you can use SQL commands to set constraints on the database environment when you connect to the database. The Data Integration Service runs the connection environment SQL each time it connects to the database.