Precedence Constraints - ( SSIS Control Flow )

Precedence Constraints provide a way to control the order in which tasks are executed in SSIS Control flow. It is a simple Boolean expression that evaluates to either success or failure, which allows tasks to execute conditionally.

Syntax

To create a Precedence Constraint in SSIS Control Flow, you need to define a logical expression that evaluates to either true or false.

• True condition: if the condition evaluates to true, the subsequent tasks are executed.
• False condition: if the condition evaluates to false, the subsequent tasks aren't executed.

Example

Suppose we have two tasks in SSIS Control Flow: TaskA and TaskB. We want TaskB to execute only if TaskA is successful.

We can create Precedence Constraint to achieve this by following the below steps:

1. Edit TaskA by right-clicking it and selecting "Edit".
2. Go to the properties window of TaskA and select the "Precedence Constraints" property.
3. Click on the green arrow to open the "Precedence Constraint Editor".
4. In the "Expression" section of the editor, select the "Success" option from the dropdown.
5. Click OK to create the Precedence Constraint.

Now TaskB will execute only if TaskA is successful.

Output

When the Precedence Constraint evaluates to true, the subsequent tasks are executed. When it evaluates to false, the subsequent tasks aren't executed.

Explanation

Precedence Constraints are used to control the order of the tasks in SSIS Control Flow. They allow for conditional task execution and can be used to create complex workflows that involve branching and decision making.

The Precedence Constraints can be edited by right-clicking the arrow that connects two tasks.

Use

Precedence Constraints can be used in a wide variety of scenarios where you need to control the order of task execution. Some common scenarios where Precedence Constraints are used include:

• Executing a task only if a specific condition is true.
• Running multiple tasks in parallel.
• Stopping the execution of a package if a certain condition is not met.

Important Points

• Precedence Constraints evaluate to either success or failure.
• The evaluation of Precedence Constraints is based on the outcome of the task that precedes them.
• Precedence Constraints can be edited by right-clicking the arrow that connects two tasks.
• Precedence Constraints are often used to conditionally execute tasks.

Summary

Precedence Constraints in SSIS Control Flow are used to control the order of task execution. They allow for conditional task execution and can be used to create complex workflows that involve branching and decision making. Precedence Constraints evaluate to either success or failure and can be edited by right-clicking the arrow that connects two tasks.