JOIN syntax knowledge — evaluate the claim:\n“SQL has a JOIN ... ON syntax that can be used to create inner joins and outer joins.” Decide whether this statement is correct or incorrect.

Introduction / Context:
Explicit JOIN syntax was standardized to make join intent clear and avoid ambiguous WHERE-based joins. The claim is that SQL provides JOIN ... ON syntax for inner and outer joins. This tests your familiarity with ANSI/ISO join notation introduced in SQL-92 and widely adopted.

Given Data / Assumptions:

• We use standard SQL keywords: INNER JOIN, LEFT/RIGHT/FULL OUTER JOIN, and ON for join predicates.
• Vendors may support additional syntaxes (e.g., USING) but they do not negate JOIN ... ON.
• We are not considering legacy proprietary outer-join operators.

Concept / Approach:
SQL supports both inner and outer joins using the JOIN ... ON form: SELECT ... FROM A INNER JOIN B ON A.key = B.key; and SELECT ... FROM A LEFT OUTER JOIN B ON .... RIGHT OUTER and FULL OUTER join forms also exist (though some engines omit FULL OUTER). Therefore, the assertion is correct in standard SQL and in the majority of modern SQL products.

Step-by-Step Solution:

Verification / Alternative check:
Write examples and observe equivalent results to legacy WHERE-based inner joins, while outer joins require the explicit OUTER JOIN forms.

Why Other Options Are Wrong:

• “Incorrect” and “proprietary only” ignore the standard.
• “WHERE for outer joins” is false; WHERE cannot generate unmatched rows from the outer table.
• “Indeterminate without ANSI mode” is misleading; most engines implement this syntax regardless of toggles.

Common Pitfalls:
Using WHERE filters that accidentally turn an outer join into an inner join; misplacing join predicates versus filtering predicates.

Final Answer:
Correct