Single-row subquery returns:
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Only one row
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Two rows
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Zero rows
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There is no such subquery
Reveal answer
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A
Correct answer
Explanation
A single-row subquery is designed to return exactly one row and one column. This type of subquery is typically used with single-row comparison operators like =, >, <, >=, or <=. If a single-row subquery returns more than one row, it will cause an error, and if it returns no rows, the result is null.
AI explanation
By definition, a single-row subquery is expected to return exactly one row (and one column) of data, so it can be used directly with single-row comparison operators like =, <, or >. If it unexpectedly returns more than one row, the database raises a runtime error rather than silently continuing.