What is fact table in database?
A fact table is the central table in a star schema of a data warehouse. A fact table stores quantitative information for analysis and is often denormalized. The foreign keys column allows joins with dimension tables, and the measures columns contain the data that is being analyzed.
What are the three types of fact tables?
There are three types of fact tables:
- Transaction Fact Table. The transaction fact table is a basic approach to operate the businesses.
- Snapshot Fact Table. The snapshot fact table describes the state of things at a particular time and contains many semi-additive and non-additive facts.
- Accumulated Fact Sheet.
What is fact table and types?
A Fact Table is a central table in a star schema of a data warehouse. A fact table works with dimension tables and it holds the data to be analyzed and a dimension table stores data about the ways in which the data can be analyzed. Thus, a fact table consists of two types of columns.
What should a fact table contain?
Fact tables contain the content of the data warehouse and store different types of measures like additive, non additive, and semi additive measures. Fact tables provide the (usually) additive values that act as independent variables by which dimensional attributes are analyzed.
How do you identify a fact table?
If a table has a composite key then it is a fact table. If a table does not have a composite key then it is a dimension table.
What is a FCT table?
The file control table (FCT) describes to CICS® the Basic Direct Access Method (BDAM) user files that are processed by file management. CICS user files correspond to physical data sets that must have been defined to MVS™ and allocated to the CICS system before they are used.
How do you create a fact table?
Steps in designing Fact Table:
- Identify a business process for analysis(like sales).
- Identify measures or facts (sales dollar).
- Identify dimensions for facts(product dimension, location dimension, time dimension, organization dimension).
- List the columns that describe each dimension.
Is fact table is Normalised?
Fact tables are completely normalized To get the textual information about a transaction (each record in the fact table), you have to join the fact table with the dimension table. Some say that fact table is in denormalized structure as it might contain the duplicate foreign keys.
How is a fact table loaded?
Fact tables are normally loaded from transaction tables such as order tables or from transactional files, such as web logs. Hence the number of rows to update or insert in a load is much larger than in dimensions. The core of loading fact tables is to change the natural keys into surrogate keys.
Do fact tables have primary keys?
The fact table also has a primary (composite) key that is a combination of these four foreign keys. As a rule, each foreign key of the fact table must have its counterpart in a dimension table. This means that every table in a dimensional database that expresses a many-to-many relationship is a fact table.