When you create tasks in SQL Server Integration Services (SSIS), you need a way to connect these tasks. Precedence constraints are the connections between the tasks that control the execution order of each task. After you create more than one task in the Control Flow in SSIS, you can then link them together by using these precedence constraints. Click once on a task, and you see a green arrow pointing down from the task. For example, in Figure 7-1 you can see a Script Task with a green arrow below the task. This is the precedence constraint arrow. These arrows control the order of tasks in a package, and they also control which tasks will run.
Figure 7-1. Figure 7-1
To create an On Success Precedence Constraint, click the green arrow coming out of the task and drag it to the task you want to link to the first task. In Figure 7-2, you can see the On Success Precedence Constraint between the two Script Tasks. Only if the first Script Task completes successfully will the second Script Task run. To delete the constraint click once on the constraint line and press Delete on the keyboard, or right-click the constraint line and left-click Delete.
Figure 7-2. Figure 7-2
The precedence constraint arrows can be different colors ...