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Data Warehousing Basics Interview Questions and Answers (4)

What is hybrid slowly changing dimension?

Hybrid SCDs are combination of both SCD 1 and SCD 2.

It may happen that in a table, some columns are important and we need to track changes for them i.e capture the historical data for them whereas in some columns even if the data changes, we don't care.

For such tables we implement Hybrid SCDs, where in some columns are Type 1 and some are Type 2.

What are the different architecture of datawarehouse?

There are two main things

1. Top down - (bill Inmon)
2.Bottom up - (Ralph kimbol)

1.what is incremintal loading?
2.what is batch processing?
3.what is crass reference table?
4.what is aggregate fact table?

Incremental loading means loading the ongoing changes in the OLTP.

Aggregate table contains the [measure] values ,aggregated /grouped/summed up to some level of hirarchy.

what is junk dimension? what is the difference between junk dimension and degenerated dimension?

Junk dimension: Grouping of Random flags and text Attributes in a dimension and moving them to a separate sub dimension.

Degenerate Dimension: Keeping the control information on Fact table ex: Consider a Dimension table with fields like order number and order line number and have 1:1 relationship with Fact table, In this case this dimension is removed and the order information will be directly stored in a Fact table inorder eliminate unneccessary joins while retrieving order information..

What are the possible data marts in Retail sales.?

Product information,sales information

What is the definition of normalized and denormalized view and what are the differences between them?

Normalization is the process of removing redundancies.

Denormalization is the process of allowing redundancies.

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