EXISTS returns true if a subquery returns at least one row. It is often faster than IN for large tables because it stops at the first match.
NOT EXISTS finds rows with no related records.
SQL EXISTS
Test whether a subquery returns rows.
✍️ 3 exercises + code challenge in this lessonKey Takeaways: SQL EXISTS
Mastering SQL EXISTS helps you write clean and reliable SQL code. Follow standard conventions, test edge cases, and keep logic simple. Try running the code example below and complete the exercises to build confidence.
SQL EXISTS Code Example
SQL-- Products that have been ordered at least once
SELECT ProductName FROM Products p
WHERE EXISTS (SELECT 1 FROM OrderItems i WHERE i.ProductID = p.ProductID);
-- Products never ordered
SELECT ProductName FROM Products p
WHERE NOT EXISTS (SELECT 1 FROM OrderItems i WHERE i.ProductID = p.ProductID);
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SQL EXISTS Practice Exercises
Check what you learned in “SQL EXISTS”.
/ 3 solved
Fill in the blank
Find customers that have at least one order.
WHERE (SELECT 1 FROM Orders o WHERE o.CustomerID = c.CustomerID)
✓ Correct!
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Multiple choice
EXISTS returns true when the subquery…
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Code challenge
Select CustomerName of customers who have never placed an order, using NOT EXISTS, sorted by name.
Write the code in the live editor. Your answer is checked automatically.
✓ Solved
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