How do you deal with late arriving Dimensions?

How do you deal with late arriving Dimensions?

Using a special “unknown” dimension

1. When the dimension data eventually does arrive, you have to remember to go back and update any fact records which are pointing at “Not known yet”.
2. You would be forced to store the natural key alongside the surrogate key in the Fact record.

What is a degenerate dimension in data warehousing?

According to Ralph Kimball, in a data warehouse, a degenerate dimension is a dimension key in the fact table that does not have its own dimension table, because all the interesting attributes have been placed in analytic dimensions. These degenerate dimensions are natural keys of the “parents” of the line items.

How does SSIS handle late arriving Dimensions?

1. Use Filtered Index on Fact Tables. Since the unknown surrogate key is well-defined subset of data, use Filtered Index to fetch fact records that have unknown SK.
2. Use Skinny Staging Tables. Fact tables usually do not store the Natural Key of the dimension.
3. Avoid Row-by-row updates.

What are different types of Dimensions in data warehouse?

Types of Dimensions are Conformed, Outrigger, Shrunken, Role-playing, Dimension to Dimension Table, Junk, Degenerate, Swappable and Step Dimensions. Five steps of Dimensional modeling are 1.

What are junk and degenerate dimensions Why is it necessary to retain them in data warehouse?

Junk dimensions are used to reduce the number of dimensions in the dimensional model and reduce the number of columns in the fact table. A junk dimension combines two or more related low cardinality flags into a single dimension. An example of this may be car color (red, black, blue, etc.)

How do you determine a degenerate dimension?

Degenerate dimensions commonly occur when the fact table’s grain is a single transaction (or transaction line). Transaction control header numbers assigned by the operational business process are typically degenerate dimensions, such as order, ticket, credit card transaction, or check numbers.

What is a surrogate key in database?

A surrogate key is a unique key for an entity in the client’s business or for an object in the database. Sometimes natural keys cannot be used to create a unique primary key of the table. This is when the data modeler or architect decides to use surrogate or helping keys for a table in the LDM.

How do you identify facts and dimensions in data warehouse?

Identifying Fact Tables (Data Warehouse)

1. Identify Subject Areas.
2. Within each subject area, identify the operational transactions that depict key business events.
3. Identify the major dimensions for each fact table.
4. Look for fact tables that contain both facts and dimensions.