A Data Warehouse is generally built using which schema for decision support?

(i) Hierarchical Schema
(ii) Star or Snowflake Schema
(iii) Relational Schema
(iv) Network Schema

Question

A Data Warehouse is generally built using which schema for decision support?

(i) Hierarchical Schema
(ii) Star or Snowflake Schema
(iii) Relational Schema
(iv) Network Schema

Accepted Answer

**Answer: (ii) Star or Snowflake Schema**

Data warehouses are optimized for read-heavy analytical queries, not transactional integrity, so they use dimensional modeling instead of normalized relational schemas.

- **Star Schema**: one central **fact table** (measures/metrics) connected directly to several **dimension tables** (denormalized, descriptive attributes).
- **Snowflake Schema**: same idea, but dimension tables are further normalized into sub-dimensions.

```
        Dim_Time        Dim_Product
             \              /
              \            /
               FACT_TABLE
              /            \
             /              \
        Dim_Customer     Dim_Store
```

Both schemas are purpose-built for OLAP-style slicing, dicing, and aggregation — which is why (ii) is correct over normalized relational schema (iii), which is used in OLTP systems.

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