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18 Cards in this Set

  • Front
  • Back

Normalization

  • Eliminates redundant data
  • Ensures dependencies make sense
  • Reduces amount of space use and makes sure data is logically stored


LOB

Line of business




Set of critical computer applications that are critical to running an enterprise. Usually ties into databases and database management systems

Data integrity

Maintaining and assuring accuracy and consistency of data over its entire life cycle

Dimensional Model vs. DW Schema

The star and snowflake schemas are within the dimensional model.

Dimension

Categorizes and describes data warehouse facts and measures in ways that support meaningful answers to business questions.



This is the context.



Should be in second normal form, or denormalized.

Fact

The measurement described by the dimensions, may be described by many dimensions.




Should be in third normal form.

Surrogate key

A primary key with no business meaning.




Only act is as the primary key.

Natural key

Key defined by the business process.




Formed by attributes in the real world

Shared/conformed dimensions

Dimensions with connections to multiple fact tables

SSAS

SQL Server Analysis Services




Performs special analysis by drilling down and is used for analyses that are based on the cube model

Denormalization

  • Attempts to optimize read performance by adding redundant data or grouping data
  • Can help cover inefficiencies in a relational database
  • Leads to better implementation of an audit trail

Granularity / dimensionality

The number of dimensions connected with a fact table defines the level of granularity.




Fact tables connected to more dimensional tables at a HIGHER level of granularity

First normal form


  1. A primary key uniquely identifies each row.
  2. Each column contains atomic values, no dupes.

Second Normal Form

  1. Is in first normal form and..
  2. All non-key columns are dependent on the table's primary key.



Narrows a table down to a single purpose.

Third Normal Form

NO......Repeated entries are removed and placed in their own snowflake to move from 2nd to 3rd.

Degenerate dimension

A dimension key in the fact table that does not have its own dimension table, because all interesting attributes have been placed in analytic dimensions.




(a dimension that remains in the fact table because there is no value gained in creating a dimension table for it)

Star schema

  • Fact table surrounded by dimension tables
  • One schema covers one business area
  • Facts are connected to dimensions by foreign keys
  • All foreign keys uniquely identify a row

Snowflake schema

A star schema with normalized dimensions




Denormalization is removed from the star by adding a snowflake dimension