Identify Considerations for Relational Data on Azure – DP-900 Study Guide
This domain accounts for 20–25% of the exam and covers relational fundamentals — tables, keys, normalization, SQL, and database objects — then the Azure services that host relational databases. The service-selection questions (Azure SQL Database vs Managed Instance vs SQL on a VM) are the highest-value target here, so this guide spends extra time on when to choose each.
Relational Concepts
The model: data lives in tables of rows and columns with a defined schema. Each row is uniquely identified by a primary key. Relationships between tables are expressed with foreign keys — a column that references another table's primary key, which the database engine can enforce (referential integrity).
Normalization organizes data so each fact is stored exactly once, splitting entities into related tables. Benefits:
- Eliminates duplication.
- Prevents update anomalies — when a duplicated fact is changed in one place but stale copies linger elsewhere.
The trade-off: more joins on read. That's fine for transactional systems (where write integrity matters most), which is exactly why analytics uses different, denormalized designs — a tension the exam likes to surface.
SQL: The Language of Relational Data
Structured Query Language falls into categories — knowing which category a statement belongs to is testable:
| Category | Statements | Purpose |
|---|---|---|
| DML (Data Manipulation) | SELECT, INSERT, UPDATE, DELETE | Read and change data (rows) |
| DDL (Data Definition) | CREATE, ALTER, DROP | Define/change structure (tables, views) |
| DCL (Data Control) | GRANT, REVOKE | Manage permissions |
| TCL (Transaction Control) | COMMIT, ROLLBACK | Control transactions |
Memory hook: DDL shapes the container; DML fills and changes what's inside. SELECT retrieves, INSERT adds, UPDATE modifies, DELETE removes.
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