How many tables can participate in a single SQL query using joins in a relational database?

Introduction / Context:
Modern SQL supports joining multiple tables within a single SELECT. From simple two-table joins to complex star schemas with many tables, understanding scalability of joins informs query design and performance expectations.

Given Data / Assumptions:

• SQL permits multiple table references in the FROM clause.
• Self-joins reference the same base table more than once (aliased), effectively increasing participating sources.
• Query planners optimize multi-join execution orders.

Concept / Approach:
There is no hard architectural limit of “two or three” tables; many joins can be chained. Even if a query references one table only, the concept of joining can be generalized (self-join or no join). In practice, databases routinely join several tables; the exact limit is system-dependent and often very high.

Step-by-Step Solution:

Verification / Alternative check:
Example queries: two-table join (A JOIN B), three-table join (A JOIN B JOIN C), and larger schemas (fact table joined to several dimensions).

Why Other Options Are Wrong:
Restricting to one, two, or three is artificially narrow; SQL supports more.

Common Pitfalls:
Complex queries can be slow without proper indexing and join predicates; always ensure selective conditions and appropriate keys.

Final Answer:
All of the above.