Explain the concept of data marts within a data warehouse.
Instruction: Describe what data marts are and their role within a larger data warehousing architecture.
Updated
Official answer
A data mart is a curated analytical dataset focused on a business subject or audience, such as marketing campaigns or finance reporting. It may contain detailed facts, aggregates or both; it need not be a physically separate database.
A dependent mart is supplied from an integrated warehouse. An independent mart draws directly from sources; a hybrid combines approaches. Independent delivery can be useful, but separate definitions of customer, revenue or reporting date can make teams' totals disagree.
For a sales mart, declare one row per order line, shared product/date dimensions, the revenue rule, freshness target and access policy. If a campaign mart attributes one order to multiple campaigns, define allocation weights or a distinct counting rule before comparing it with finance revenue.
Use governed transformations, lineage and reconciliations so the subject-specific view remains understandable and trustworthy. A mart can simplify user queries or isolate workloads, but reduced scope alone does not guarantee faster execution. Measure physical performance and freshness, and retain an owner for changes to its business definitions.