Please show the employee first names and ids of employees who serve at least 10 customers?
SELECT T1.FirstName , T1.SupportRepId FROM CUSTOMER AS T1 JOIN EMPLOYEE AS T2 ON T1.SupportRepId  =  T2.EmployeeId GROUP BY T1.SupportRepId HAVING COUNT ( * )   > =   10
employees who serve at least 10 customers refers to HAVING COUNT(*) >= 10; employee first names and ids refers to SELECT FirstName, EmployeeId;