Exists
The EXISTS command tests for the existence of any record in a subquery, and returns true if the subquery returns one or more records.
The following SQL lists the suppliers with a product price less than 20:
Example
SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM
Products WHERE SupplierId = Suppliers.supplierId AND Price < 20);The following SQL lists the suppliers with a product price equal to 22:
Example
SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM
Products WHERE SupplierId = Suppliers.supplierId AND Price = 22);