Joining Multiple Tables Flashcards
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Which JOIN type returns all rows from the left table and matching rows from the right table, with NULLs for non-matches?
Answer: LEFT OUTER JOIN
LEFT OUTER JOIN returns all rows from the left table and matched rows from the right; unmatched right columns are NULL.
What is the result of a CROSS JOIN between a table with 4 rows and a table with 3 rows?
Answer: 12 rows
A CROSS JOIN (Cartesian product) returns every combination, so 4 × 3 = 12 rows.
Which SQL syntax represents an ANSI-standard INNER JOIN?
Answer: SELECT * FROM a JOIN b ON a.id = b.id
The ANSI JOIN syntax uses the JOIN keyword with an ON clause to specify the join condition.
What is a NATURAL JOIN in Oracle SQL?
Answer: A join that uses all columns with the same name in both tables
NATURAL JOIN automatically joins tables on all columns that share the same name and compatible data type.
Which clause in a JOIN allows you to specify a single common column name without a table prefix?
Answer: USING
The USING clause specifies a common column by name, and that column cannot be prefixed with a table alias.
What type of join returns rows from both tables regardless of whether a match exists?
Answer: FULL OUTER JOIN
FULL OUTER JOIN returns all rows from both tables, with NULLs where there is no matching row.