Star Schema and Extended Star Schema

Star Schema:
Star Schema can be defined as the collection of database objects which includes the tables, views, indexes and synonyms. Star schema can also be defined as a relational database which also represents the fields in relational database. The relationship between the fields and the tables are also defined. This is the simplest form of a dimensional model of data which is based on fact table. The fact table is covered by few dimension tables in the form of star. Hence the name Star Schema is arrived to the specific data model. In business terms it is called as the method of organizing information in a data warehouse.

InfoCube consists of different Info-Object which are arranged according to the star schema. An InfoCube is formed by combining the dimensions and it can have a maximum 16 dimensions for one fact table.
Extended Star Schema:
Many issues existing in the usage of Star Schema are resolved in the Extended Star schema. In this schema, fact table and the master table are connected through a Surrogate ID table which is called as SID table. Both fact table and the dimension table are placed inside the Infocube and having a analyzing capacitu of 16*248 (SID Table). The size of the Fact table is small where dimension table is big which is opposite to the previous Star schema model. The difference between both models is consisting of master data in dimension table in the Star Schema where the dimension table does not contain master data in the Extended Star Schema. The master data is reusable here as it is outside of the Infocube.

Star Schema Vs Extended Star Schema
Star Schema :
• Master data table exists inside the Infocube.
• Star Schema considers 16 angles.
• Performace is slow due to Alpha-Numeric.
• Dimension and master data tables are same since one dimension table = one master data table.
• Master data cannot be reused.
Extended Star Schema:
• Master data table is outside of the Infocube.
• Performance is fast due to SIDs.
• Master data can be reused.
• Dimension and master data table are not same. One dimension table = 248 master data tables.