Professional SQL Server™ 2005 Integration Services

1.3. Precedence Constraints

Precedence constraints direct the tasks to execute in a given order. They direct the workflow of your SSIS package based on given conditions. Precedence constraints have been enhanced dramatically in SQL Server 2005 Integration Services conditional branching of your workflow based on conditions.

1.3.1. Constraint Value

Constraint values are the type of precedence constraint that you may be familiar with in SQL Server 2000. There are three types of constraint values:

• Success: A task that's chained to another task with this constraint will execute only if the prior task completes successfully.

• Completion: A task that's chained to another task with this constraint will execute if the prior task completes. Whether the prior task succeeds or fails is inconsequential.

• Failure: A task that's chained to another task with this constraint will execute only if the prior task fails to complete. This type of constraint is usually used to notify an operator of a failed event or write bad records to an exception queue.

1.3.2. Conditional Expressions

The nicest improvement to precedence constraints in SSIS 2005 is the ability to dynamically follow workflow paths based on certain conditions being met. These conditions use the new conditional expressions to drive the workflow. An expression allows you to evaluate whether certain conditions have been met before the task is executed and the path followed. The constraint evaluates only the success or failure of the previous ...