Which statement describes an inner join?

Which statement describes an inner join?

• A. It returns all rows from the left table regardless of matches
• B. It returns rows only where there is a match in both tables
• C. It returns all rows from both tables regardless of matches
• D. It returns the result of a cartesian product

Answer: (B)

Inner join is used to combine two tables by matching values in the join condition and returns only the rows where there is a match in both tables. For example, joining customers and orders on a customer_id yields only orders that reference an existing customer; orders with a nonmatching customer_id are omitted. This is different from a left outer join, which returns all rows from the left table regardless of matches (filling in nulls for missing right-side data), a full outer join, which returns all rows from both tables (with nulls where there is no match), and a cross join, which pairs every row of one table with every row of the other.

Inner join is used to combine two tables by matching values in the join condition and returns only the rows where there is a match in both tables. For example, joining customers and orders on a customer_id yields only orders that reference an existing customer; orders with a nonmatching customer_id are omitted. This is different from a left outer join, which returns all rows from the left table regardless of matches (filling in nulls for missing right-side data), a full outer join, which returns all rows from both tables (with nulls where there is no match), and a cross join, which pairs every row of one table with every row of the other.