Query using INNER JOIN obviously satisfies the requirements as it perfoms exactly what is needed.
Query using FULL OUTER JOIN also meets requirements as it joins all records (even those that do not have match in second table), but all unmatched records are truncated by WHERE T1.p_key IS NOT NULL AND T2.f_key IS NOT NULL condition.
Queries using LEFT OUTER JOIN and RIGHT OUTER JOIN are analagous to FULL OUTER JOIN query and, therefore, satisfy the requirement.
Query using WHERE T1.p_key = T2.f_key condition is identical to an INNER JOIN query as well. So, it also meets requirements.
UNION ALL is the only one that does not satisfy requirements as instead of joining two tables it performs their union returning one column containing data from both tables.
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