When working with SQL Server, there are times when you need to use variables in your data flow. However, currently, none of the existing Data Flow sources allow you to source variables. In this blog post, we will explore a workaround to this limitation and show you how to use variables in a Data Flow component.

Let’s say you have a stored procedure that returns a single record, and you want to use the output of this stored procedure as variables in your data flow. The first step is to create the stored procedure with output parameters. These output parameters will be mapped to SSIS variables.

CREATE PROCEDURE GetRecord
    @Output1 INT OUTPUT,
    @Output2 VARCHAR(50) OUTPUT
AS
BEGIN
    -- Your logic here
END

Once you have the stored procedure set up, you can execute it and store the output in SSIS variables. This can be done using a Script Task Source component.

Next, you need to create a custom Script Component to introduce the variables into the data flow. In the Script Component, you will define the output columns that correspond to the variables filled in by the stored procedure.

There are two ways to introduce the variables into the script component. The first way is to list them in the read-only section of the script component. However, in this example, we will use the VariableDispenser object to work with the variables.

Once the variables are introduced into the script component, you can pass them down using the CreateNewOutputRows() method available to a Script Source Component. Each package variable is added to the corresponding output variable built off the Script Source Component for use by any component within the Data Flow Task.

Now you might be wondering, why would you want to use variables in a Data Flow? One reason is performance. By working on a single record at a time, you can optimize the workflow and improve speed. For example, if you are processing hundreds of PDF files from a directory, it may be more efficient to work on one document at a time.

Additionally, there may be cases where you cannot directly select the next record to import from a queue table. In such scenarios, using a stored procedure to retrieve the next record and remove it from the queue becomes necessary.

By leveraging variables in your SQL Server Data Flow, you can overcome the limitations of existing Data Flow sources and optimize your workflow for better performance.

We hope this blog post has provided you with valuable insights into using variables in SQL Server Data Flow. Stay tuned for more SQL Server tips and tricks!