Star schema one of the very commonly used style of data warehouse schema. The star schema consists of a few fact tables (possibly only one, justifying the name) referencing any number of dimension tables. The star schema is considered an important special case of the snowflake schema. Note that in star schema different dimensions are not related to one another.

Star schema illustration

Above diagram inllustrates how the schema looks like, the name "star" is because of the central entity surrounded by other entities which resembles the star.

All measures in the fact table are related to all the dimensions that fact table is related to. In other words, they all have the same level of granularity.

A star schema can be simple or complex. A simple star consists of one fact table; a complex star can have more than one fact table.

Let's look at an example: Assume our data warehouse keeps store sales data, and the different dimensions are time, store, product, and customer. In this case, the sales fact table will be at the center of the diagram(above) and the dimension tables time, store, product, customer will be surrounded and are connected to fact table with primary key-foreign key relationship.