Which are two applications not suitable for SQL?

• A. Small data sets and simple joins.
• B. Data with fixed schema and flat files.
• C. Infinitely sized database and recursive queries.
• D. In-memory caches and log files.

Answer: (C)

SQL works best with structured, finite data and operations that act on whole sets of rows. When data could grow without bound, defining and maintaining a scalable, well-indexed relational model becomes impractical, so an infinitely sized database isn’t a good fit for SQL. Similarly, deeply nested or graph-like relationships require recursive traversal; while some SQL dialects offer recursion features, they’re not as natural or efficient for large or complex recursive hierarchies as tools designed for graph processing. That’s why those two scenarios aren’t ideal for SQL. The other options align more with SQL strengths: small data sets with simple joins, or data with a fixed schema that can be loaded into a relational model.