Has Alex purchased product with id 498?
WHEN ProductID = 498 AND FirstName = 'Alex' means that Alex purchased a product; WHEN ProductID = 498 AND FirstName NOT 'Alex' means Alex has not purchased a product;
SELECT IIF(T1.ProductID = 498, 'YES', 'NO') FROM Sales AS T1 INNER JOIN Customers AS T2 ON T1.CustomerID = T2.CustomerID WHERE T2.FirstName = 'Alex'
database name:db_id sales
Customers table Customers Cols: Customer ID dtype integer, First Name dtype text, Middle Initial dtype text, Last Name dtype text, 
Employees table Employees Cols: Employee ID dtype integer, First Name dtype text, Middle Initial dtype text, Last Name dtype text, 
Products table Products Cols: Product ID dtype integer, Name dtype text, Price dtype real, 
Sales table Sales Cols: Sales ID dtype integer, SalesPerson ID dtype integer, Customer ID dtype integer, Product ID dtype integer, Quantity dtype integer, 
