List the first names of customers who have purchased products from sale person id 1.
SELECT T1.FirstName FROM Customers AS T1 INNER JOIN Sales AS T2 ON T1.CustomerID = T2.CustomerID WHERE T2.SalesPersonID = 1
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, 
