How many fact tables are in a star schema?
one fact table
A star schema consists of one fact table, and one or more dimension tables. The fact table contains information about changes. In the most basic kind of fact table, each row represents a transaction.
How many dimension tables are there in a star schema?
one dimension table
Each star schema database has at least one dimension table, but will often have many. Each dimension table will relate to a column in the fact table with a dimension value, and will store additional information about that value.
What is the relationship between dimension and fact table in star schema?
A fact table contains dimension key columns that relate to dimension tables, and numeric measure columns. The dimension key columns determine the dimensionality of a fact table, while the dimension key values determine the granularity of a fact table.
What is a fact table in a star schema?
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. A fact table works with dimension tables.
Can we have two fact tables in a star schema?
Although the diagram in this chapter shows a single fact table, a star schema can have multiple fact tables. A more complex schema with multiple fact tables is useful when you need to keep separate sets of measurements that share a common set of dimension tables.
What are the dimensions of a star schema?
Time dimension table contains the attributes: Order ID, Order Date, Year, Quarter, Month. In Star Schema, Business process data, that holds the quantitative data about a business is distributed in fact tables, and dimensions which are descriptive characteristics related to fact data.
How often is data extracted from a star schema?
A snapshot of the source data is regularly extracted and moved to the data mart, usually at the same time every day, every week, or every month. Although the diagram in this chapter shows a single fact table, a star schema can have multiple fact tables.
What is the difference between a star schema and a snowflake schema?
In Data Warehouse Modeling, a star schema and a snowflake schema consists of Fact and Dimension tables. Fact Table: It contains all the primary keys of the dimension and associated facts or measures(is a property on which calculations can be made) like quantity sold, amount sold and average sales.
How is star schema used in data warehouse modeling?
This schema is widely used to develop or build a data warehouse and dimensional data marts. It includes one or more fact tables indexing any number of dimensional tables. The star schema is a necessary cause of the snowflake schema. It is also efficient for handling basic queries.