Among the sales people, who are hired prior to 2010?
Sales people refer to PersonType = 'SP'; hired prior to 2010 means the person's hiring date was before 2010, therefore year(HireDate)<2010
SELECT COUNT(T1.BusinessEntityID) FROM Employee AS T1 INNER JOIN Person AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID WHERE T2.PersonType = 'SP' AND SUBSTR(T1.HireDate, 0, 4) < 2010