The document discusses slowly changing dimensions and the different types of changes that can occur in dimension attributes during an extract, transform, load (ETL) process. It describes fixed attributes, which should not change value; changing attributes, which overwrite existing records; and historical attributes, which create new records instead of updating existing ones. Historical changes are directed to two outputs to insert new records and flag the previous record as expired. The slowly changing dimension transformation supports these different change types and directs rows to the appropriate outputs.

1. Implementing an Incremental ETL Process
Ram Kedem

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Slowly Changing Dimension Transformation
•The Slowly Changing Dimension transformation coordinates the updating and inserting of records in data warehouse dimension tables.
•The Slowly Changing Dimension Wizard only supports connections to SQL Server.
•The Slowly Changing Dimension transformation supports four types of changes: fixed attribute, changing attribute, historical attribute, and inferred member.

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Fixed Attribute
•Fixed attribute changes indicate the column value must not change. The Slowly Changing Dimension transformation detects changes and can direct the rows with changes to an output named Fixed Attribute Output.

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Inferred Dimension Members
•Use the Inferred Dimension Members dialog box to specify options for using inferred members. Inferred members exist when a fact table references dimension members that are not yet loaded.
•When data for the inferred member is loaded, you can update the existing record rather than create a new one.
•If you choose to enable inferred members, you must select one of the two options that follow
•All columns with a change type are null -Specify whether to enter null values in all columns with a change type in the new inferred member record.
•Use a Boolean column to indicate whether the current record is an inferred member -Specify whether to use an existing Boolean column to indicate whether the current record is an inferred member.

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Fixed Attribute

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Fixed Attribute

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Fixed Attribute

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Changing attribute
•Changing attribute changes overwrite existing records.
•The Slowly Changing Dimension transformation directs these rows to an output named Changing Attributes Updates Output.

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Changing attribute

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Changing attribute

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Changing attribute

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Changing attribute

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Changing attribute

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Changing attribute

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Changing attribute

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Changing attribute

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Changing attribute

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Historical Attribute
•Historical attribute changes create new records instead of updating existing ones. The only change that is permitted in an existing record is an update to a column that indicates whether the record is current or expired.
•The Slowly Changing Dimension transformation directs these rows to two outputs: Historical Attribute Inserts Output and New Output

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Current Row

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date

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Historical Attribute with Start / End Date