201. What is database federation?
- a) Querying multiple databases as one
- b) Replicating data globally
- c) Encrypting distributed data
- d) Partitioning across servers
Answer: A - Enables unified access to heterogeneous data sources (SQL Server Linked Servers, PostgreSQL FDWs).
202. Which SQL feature enables continuous data ingestion?
- a) Change Data Capture (CDC)
- b) Streaming inserts
- c) Materialized views
- d) All of the above
Answer: D - Modern databases support real-time data pipelines.
203. What is an immutable database log?
- a) Append-only transaction record
- b) Encrypted backup
- c) Read-only snapshot
- d) Blockchain table
Answer: A - Foundational for audit trails and event sourcing (WAL in PostgreSQL).
204. Which database supports HTAP (Hybrid Transactional/Analytical Processing)?
- a) SQL Server with Columnstore
- b) Oracle In-Memory
- c) SAP HANA
- d) All of the above
Answer: D - Process transactions and analytics simultaneously.
205. What is the purpose of verifiable credentials in blockchain databases?
- a) Tamper-proof identity verification
- b) Encrypted backups
- c) Query authentication
- d) Schema validation
Answer: A - Uses decentralized identifiers (DIDs) for trustless verification.
206. Which statement creates a foreign data wrapper?
- a) CREATE FOREIGN DATA WRAPPER
- b) MAKE EXTERNAL CONNECTOR
- c) ADD DATA LINK
- d) DEFINE FEDERATION
Answer: A - PostgreSQL extension for querying external data.
207. What is the purpose of the SQL STREAMING INSERT statement?
- a) High-throughput continuous data loading
- b) Video data storage
- c) Network packet capture
- d) Memory buffering
Answer: A - Snowflake/Kafka integrations use this pattern.
208. Which database provides built-in ledger verification?
- a) SQL Server Ledger
- b) Oracle Blockchain Table
- c) Amazon QLDB
- d) All of the above
Answer: D - Cryptographically verifiable data integrity.
209. What is the purpose of the SQL GENERATE_UUID() function?
- a) Creates universally unique identifiers
- b) Generates encryption keys
- c) Produces random samples
- d) Hashes data
Answer: A - Standardized 128-bit unique IDs (UUID v4 in PostgreSQL).
210. Which feature enables cross-cloud database queries?
- a) Database federation
- b) Data virtualization
- c) Cloud vendor extensions
- d) All of the above
Answer: D - Example: Querying AWS RDS from Azure SQL.
211. What is the purpose of the SQL VERIFY_LEDGER() function?
- a) Validates blockchain table integrity
- b) Checks encryption
- c) Tests permissions
- d) Audits logs
Answer: A - SQL Server's ledger verification stored procedure.
212. Which statement creates a continuous aggregate?
- a) CREATE MATERIALIZED VIEW...WITH CONTINUOUS REFRESH
- b) MAKE LIVE AGGREGATE
- c) ENABLE REAL-TIME SUMMARY
- d) DEFINE ROLLUP TABLE
Answer: A - TimescaleDB feature for time-series analytics.
213. What is the purpose of the SQL DIFFERENTIAL() function?
- a) Compares sequential values
- b) Calculates derivatives
- c) Tests data variance
- d) Validates changes
Answer: A - Used in time-series analysis (InfluxDB/SQL extensions).
214. Which database provides native graph pattern matching?
- a) Neo4j
- b) SQL Server 2022+
- c) Oracle PGX
- d) All of the above
Answer: D - Specialized syntax for relationship traversal.
215. What is the purpose of the SQL SHOW_CHANGES() function?
- a) Returns CDC records
- b) Displays DDL history
- c) Tracks performance drift
- d) Logs user activity
Answer: A - Snowflake's change tracking accessor.
216. Which statement enables database sharding?
- a) CREATE SHARD
- b) ENABLE HORIZONTAL PARTITIONING
- c) DISTRIBUTE TABLE
- d) Implementation-specific
Answer: D - MongoDB/Citus use different syntax than Oracle Sharding.
217. What is the purpose of the SQL APPROX_MEDIAN() function?
- a) Estimates median with low memory
- b) Calculates exact median
- c) Samples middle values
- d) Tests distribution
Answer: A - Probabilistic algorithm for large datasets (Oracle).
218. Which database provides built-in time-series forecasting?
- a) TimescaleDB
- b) InfluxDB
- c) SQL Server ML Services
- d) All of the above
Answer: D - ARIMA, Prophet, and other models integrated.
219. What is the purpose of the SQL CREATE CREDENTIAL statement?
- a) Stores authentication secrets
- b) Generates certificates
- c) Defines permissions
- d) Encrypts data
Answer: A - Securely manages external data source credentials.
220. Which feature enables database version control?
- a) Liquibase/Flyway
- b) Git integration
- c) Schema snapshots
- d) All of the above
Answer: D - Manage schema changes like application code.