WHERE ???

???

-- ??????????????????????????????????????????????????????
-- ?????????????????????
SELECT *
FROM FlightAvailability
WHERE business_seats_taken IS NULL
OR business_seats_taken = 0
-- EMP_ACT???EMPLOYEE??????????????????????????????
-- EMP_ACT???????????????EMPLOYEE????????????????????????(LASTNAME)????????????
-- ???????????????????????????
SELECT SAMP.EMP_ACT.*, LASTNAME
  FROM SAMP.EMP_ACT, SAMP.EMPLOYEE
  WHERE EMP_ACT.EMPNO = EMPLOYEE.EMPNO
-- ????????????????????????????????????????????????????????????????????????????????????????????????
--?????????
-- ????????????????????????????????????????????????(DINFO)?????????AS????????????????????????????????????
-- AVGSALARY???EMPCOUNT????????????WHERE????????????????????????DEPTNO???
-- ????????????????????????????????????????????????
SELECT THIS_EMP.EMPNO, THIS_EMP.SALARY, DINFO.AVGSALARY, DINFO.EMPCOUNT
 FROM EMPLOYEE THIS_EMP,
   (SELECT OTHERS.WORKDEPT AS DEPTNO,
           AVG(OTHERS.SALARY) AS AVGSALARY,
           COUNT(*) AS EMPCOUNT
    FROM EMPLOYEE OTHERS
    GROUP BY OTHERS.WORKDEPT
   )AS DINFO
 WHERE THIS_EMP.JOB = 'SALESREP'
	   AND THIS_EMP.WORKDEPT = DINFO.DEPTNO