Left join returns records from the left table even if there are no matching records in the right table?

Left join returns records from the left table even if there are no matching records in the right table?

• A. Right join returns unmatched from left
• B. Left join returns all records from the right table
• C. Left join returns records from the left table even if there are no matching records in the right table
• D. Left join is the same as a cross join

Answer: (C)

The behavior being tested is how a left join preserves every row from the left table while bringing in matching data from the right table. For each row in the left table, the database looks for corresponding rows in the right table. If a match exists, you get the combined data; if there isn’t a match, you still keep the left table row, and the right-side columns appear as NULL. This exactly describes the statement: a left join returns records from the left table even if there are no matching records in the right table. A helpful way to see this is imagining customers and their orders. Every customer appears, but if a customer has no orders, you’ll still see that customer row with NULLs in the order fields. Why the other ideas don’t fit: a right join would preserve all rows from the right table, not the left; a left join returning all records from the right table would miss the point of the left side. A left join is not the same as a cross join, which would produce every possible combination of rows from both tables regardless of any relationship.

The behavior being tested is how a left join preserves every row from the left table while bringing in matching data from the right table. For each row in the left table, the database looks for corresponding rows in the right table. If a match exists, you get the combined data; if there isn’t a match, you still keep the left table row, and the right-side columns appear as NULL.

This exactly describes the statement: a left join returns records from the left table even if there are no matching records in the right table. A helpful way to see this is imagining customers and their orders. Every customer appears, but if a customer has no orders, you’ll still see that customer row with NULLs in the order fields.

Why the other ideas don’t fit: a right join would preserve all rows from the right table, not the left; a left join returning all records from the right table would miss the point of the left side. A left join is not the same as a cross join, which would produce every possible combination of rows from both tables regardless of any relationship.