In a JOIN, what clause specifies how rows from two tables are matched?

• A. The USING clause.
• B. The ON clause.
• C. The WHERE clause.
• D. The GROUP BY clause.

Answer: (B)

When joining two tables, the ON clause provides the condition that determines how rows from the two tables are matched. It specifies which columns to compare and what relationship must hold for a pair of rows to be joined, such as ON employees.dept_id = departments.id. The USING clause is a shorthand form used when the joined tables have the same-named columns you want to match on, still defining the match in a simpler way. The WHERE clause filters rows after the join is formed, so it affects which results appear rather than how rows are matched. The GROUP BY clause aggregates results after the join, not the matching process.