What is required for an inner join?

What is required for an inner join?

• A. Relationships must match in both tables
• B. Not necessary to have related fields
• C. Non-matching records are included
• D. Full outer join semantics

Answer: (A)

An inner join returns only rows where there is a match between the two tables on the join condition, so related fields must align in both tables. That means the key values on one side must have corresponding values on the other side to appear in the result. If there’s no match, those rows are excluded, which is why non-matching records aren’t included by an inner join. If you need to include non-matching rows, you’d use an outer join instead. For example, joining employees to departments on department_id will include only employees whose department_id exists in the departments table. Nulls in the join keys typically don’t satisfy the match, so those rows won’t appear.

An inner join returns only rows where there is a match between the two tables on the join condition, so related fields must align in both tables. That means the key values on one side must have corresponding values on the other side to appear in the result. If there’s no match, those rows are excluded, which is why non-matching records aren’t included by an inner join. If you need to include non-matching rows, you’d use an outer join instead. For example, joining employees to departments on department_id will include only employees whose department_id exists in the departments table. Nulls in the join keys typically don’t satisfy the match, so those rows won’t appear.