In an SQL SELECT statement, how must a subquery be enclosed syntactically?

Introduction / Context:
Subqueries are nested SELECT statements that return intermediate results to the outer query. They are commonly used in WHERE, FROM, and SELECT clauses.

Given Data / Assumptions:

• We are working with standard SQL syntax.
• We must identify the delimiter required for enclosing subqueries.

Concept / Approach:
SQL syntax requires subqueries to be enclosed in parentheses. This groups the subquery as a unit, distinguishing it from the main query.

Step-by-Step Solution:

Verification / Alternative check:
ANSI SQL documentation shows parentheses around subqueries in all valid examples.

Why Other Options Are Wrong:
Braces/brackets: Not part of SQL subquery syntax.
CAPITAL LETTERS: SQL is case-insensitive, but capitalization does not define subqueries.

Common Pitfalls:
Confusing SQL with programming languages that use braces or brackets.

Final Answer:
parenthesis -- (...)