Why is indexing important in a data warehouse?

• A. It makes the data warehouse look more organized.
• B. It speeds up data retrieval times.
• C. It helps in cleaning the data.
• D. It reduces storage usage.

Answer: (B)

Indexing is all about speeding data access. By building a fast lookup structure on columns that queries frequently filter on or join through, the database can jump straight to the relevant rows rather than scanning every row in a huge table. In a data warehouse, where tables can be enormous, this reduces disk I/O dramatically and shortens query times, especially for selective predicates and join conditions. Different index types are used to balance performance and maintenance; bitmap indexes, for example, are common for low-cardinality columns because they efficiently support filtering without heavy update costs.

Note that the other options miss the essential purpose: indexing isn’t about making the warehouse look organized, cleaning the data, or reducing storage usage. In fact, indexes add storage and maintenance overhead during loading and updates.