Chapter 5. The Data Flow

In the last two chapters you were introduced to the Control Flow tab through tasks and containers. In this chapter, you'll continue along those lines with an exploration of the Data Flow tab, which is where you'll spend most of your time as an SSIS developer. The Data Flow Task is where the bulk of your data heavy lifting will occur in SSIS. This chapter walks you through how each transformation in the Data Flow Task can help you move and clean your data.

The Data Flow

One of the toughest concepts to understand for a new SSIS developer is the difference between the Control Flow and Data Flow tabs. Chapter 2 goes into this further, but just to restate a piece of that concept, the Control Flow tab controls the workflow of the package and the order of when each task will execute. Each task in the Control Flow has a user interface to configure the task with the exception of the Data Flow Task. The Data Flow Task is configured in the Data Flow tab. Once you drag a Data Flow Task over onto the Control Flow tab and double-click it to configure it, you're immediately taken to the Data Flow tab.

The Data Flow is made up of three components that will be discussed in this chapter: sources, transformations (also known as transforms), and destinations. These three components make up the fundamentals of ETL. Sources extract data out of flat files, OLE DB databases, and other locations. Transforms process the data once it has been pulled out, and destinations write the data ...

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