STAR SCHEMA AND SNOWFLAKE SCHEMA AND THEIR DIFFERENCES.

In SQL, when designing data warehouses and business intelligence solutions, two common schema designs are used to organize fact and dimension tables:STAR SCHEMA.- One central fact table.- Multiple dimension tables connected directly to the fact table.- Each dimension table is connected to the fact table through a foreign key.- Resembles a star shape, with the fact table at the center.Example:Fact table: Sales.Dimension tables: Customer, Product, Date, Region.SNOWFLAKE SCHEMA.- One central fact table.- Dimension tables are further divided into multiple related tables.- Each dimension table is connected to the fact table through a foreign key, and also has its own related tables.- Resembles a snowflake shape, with the fact table at the center and multiple layers of related tables.Example:Fact table: Sales.Dimension tables: Customer (connected to Address, Contact), Product (connected to Category, Subcategory), Date (connected to Month, Year).In simple terms:- Star Schema is like a simple hub-and-spoke design, where each dimension is directly connected to the fact table.- Snowflake Schema is like a more detailed, layered design, where each dimension has its own related tables, creating a hierarchical structure.Both designs have their uses, and the choice depends on the specific data warehousing needs and complexity of the data.DIFFERENCES BETWEEN STAR SCHEMA AND SNOWFLAKE SCHEMA.STAR SCHEMA:- Each dimension is represented by a single table.- Dimension tables are denormalized, containing all attributes for that dimension.- Fact table is connected to each dimension table directly.- Easier to query and maintain.- Less storage space required.SNOWFLAKE SCHEMA:- Each dimension is represented by multiple tables.- Dimension tables are normalized, with each table containing only related attributes.- Fact table is connected to main dimension tables, which are connected to additional dimension tables.- More complex to query and maintain.- More storage space required.In summary:- STAR SCHEMA is simpler, with fewer tables and less storage needed, but may contain redundant data.- SNOWFLAKE SCHEMA is more complex, with more tables and more storage needed, but eliminates data redundancy.CHOOSE STAR SCHEMA for:- Simple data models.- Fast query performance.- Less data redundancy.CHOOSE SNOWFLAKE SCHEMA for:- Complex data models.- Minimal data redundancy.- Improved data integrity.