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SELECT DEPARTMENT_ID, COUNT (*) FROM EMPLOYEES GROUP BY DEPARTMENT_ID;
SELECT DEPARTMENT_ID, JOB_ID, SUM (SAL) FROM EMPLOYEES GROUP BY DEPARTMENT_ID, JOB_ID;
SELECT SUM (SALARY) FROM EMPLOYEES GROUP BY DEPARTMENT_ID, JOB_ID;
SELECT JOB_ID, SUM (SALARY) FROM EMPLOYEES WHERE JOB_ID > 100 GROUP BY JOB_ID HAVING SUM (SALARY) > 10000;