What is the difference between a fact table and a dimension table?

Posted on by Emilia Duggan

What is the difference between a fact table and a dimension table?

A fact table holds the data to be analyzed, and a dimension table stores data about the ways in which the data in the fact table can be analyzed. Thus, the fact table consists of two types of columns.

Which dimension is slowly changing?

What is a Slowly Changing Dimension? A Slowly Changing Dimension (SCD) is a dimension that stores and manages both current and historical data over time in a data warehouse. It is considered and implemented as one of the most critical ETL tasks in tracking the history of dimension records.

What is difference between SCD1 and SCD2?

Type 1 dimension mapping (SCD1): This keeps only current data and does not maintain historical data. Note : Use SCD1 mapping when you do not want history of previous data. Type 2 dimension/version number mapping (SCD2): This keeps current as well as historical data in the table.

What is the difference between slowly changing dimensions Type 1 and Type 2?

You do not need to specify any additional information to create a Type 1 SCD. A Type 2 SCD retains the full history of values. When the value of a chosen attribute changes, the current record is closed. A new record is created with the changed data values and this new record becomes the current record.

How do models slowly changing dimensions?

What are Slowly Changing Dimensions?

  1. Type 0 – The passive method.
  2. Type 1 – Overwriting the old value.
  3. Type 2 – Creating a new additional record.
  4. Type 3 – Adding a new column.
  5. Type 4 – Using historical table.
  6. Type 6 – Combine approaches of types 1,2,3 (1+2+3=6)

What is factless fact table why we need it?

Factless fact tables are only used to establish relationships between elements of different dimensions. And are also useful for describing events and coverage, meaning tables contain information that nothing has happened. It often represents many-to-many relationships. The only thing they have is an abbreviated key.

What is the relationship between fact and dimension tables?

A dimension table contains a surrogate key, natural key, and a set of attributes. On the contrary, a fact table contains a foreign key, measurements, and degenerated dimensions. Dimension tables provide descriptive or contextual information for the measurement of a fact table.