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In the star schema design, a single object (the fact table) sits in the middle and is radially connected to other surrounding objects (dimension lookup tables) like a star. Each dimension is represented as a single table. The primary key in each dimension table is related to a forieng key in the fact table.
Sample star schema
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 figure on the left repesents our star schema. The lines between two tables indicate that there is a primary key / foreign key relationship between the two tables. Note that different dimensions are not related to one another.