Intermediate
Database Management Systems
Q74 / 100
What is an anti-join in SQL?
Correct! Well done.
Incorrect.
The correct answer is C) A query pattern (typically using NOT EXISTS or LEFT JOIN ... WHERE right.col IS NULL) that returns rows from one table that have no matching rows in another table
C
Correct Answer
A query pattern (typically using NOT EXISTS or LEFT JOIN ... WHERE right.col IS NULL) that returns rows from one table that have no matching rows in another table
Explanation
Anti-joins find "rows in A without a match in B" — for example, customers who have never placed an order. NOT EXISTS and LEFT JOIN/IS NULL are common implementations, and the optimizer can rewrite NOT IN into an efficient anti-join plan.
Progress
74/100