Datasheet

Figure 1-10: Changing the Column delimiter
Precedence Constraints
Precedence constraints are the conductor for your workflow. They dictate which tasks will execute and
in what order. Precedence constraints appear as lines in the control flow that connect one or more
tasks together. The green arrow represents On Success and means that the second (or downstream)
task will only execute if the first (or upstream) task or set of tasks executes successfully. The blue
arrow represents On Completion and means that regardless of whether the upstream task completes
successfully or fails, the downstream task will execute. This is useful for a clean-up task, for example.
The red arrow represents On Failure and means that the downstream task will execute only if the
upstream task fails.
You can also place expressions on the precedence constraint. With this functionality, you can put code on
the constraint that states that the expressions must be true, and optionally the constraint must be true as
well. These are useful if you want to add conditions into your control flow.
Returning to the example application, go to the Control Flow tab and drag over a Script Task onto the
design pane. Rename the task to Stub Code and drag the green arrow out of the Data Flow Task onto the
Script Task. Drag over one more Script Task and call it Stub Code 2. Drag the green arrow out of both of
the other tasks onto Stub Code 2. These tasks will act only as placeholders for future code. The control
flow should now look like Figure 1-11. Currently, Stub Code 2 will execute only after the first two tasks
successfully execute.
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Chapter 1: Getting Started
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