CREATE TABLE CUSTOMER (FirstName VARCHAR, SupportRepId VARCHAR)
CREATE TABLE EMPLOYEE (EmployeeId VARCHAR)

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
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