How many people with the name Alex are single and occupying organization level of 1?
Alex refers to FirstName = 'Alex'; single refers to MaritalStatus = 'S'
SELECT COUNT(T1.BusinessEntityID) FROM Employee AS T1 INNER JOIN Person AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID WHERE T2.FirstName = 'Alex' AND T1.MaritalStatus = 'S' AND T1.OrganizationLevel = 1