SELECT DEPTNO,JOB,AVG(SAL) AS [MESOS_MISTHOS]
FROM EMP
GROUP BY DEPTNO,JOB
ORDER BY DEPTNO;

SELECT JOB,MAX(SAL) AS [MAX SAL]
FROM EMP
GROUP BY JOB;

SELECT JOB,MAX(SAL) AS [MAX SAL]
FROM EMP
GROUP BY JOB
HAVING MAX(SAL)>=3000;

SELECT JOB,MAX(SAL) AS [MAX SAL],MIN(SAL) AS [MIN  SAL],AVG(SAL) AS [AVG SAL]
FROM EMP
GROUP BY JOB;

SELECT DEPTNO,AVG(SAL) AS [AVERAGE]
FROM EMP
GROUP BY DEPTNO
HAVING AVG(SAL)>2000;


SELECT COUNT(JOB) AS [PLHTHOS]
FROM EMP
WHERE JOB LIKE 'MANAGER';

SELECT DEPTNO,COUNT(DEPTNO) AS [ATHRISMA]
FROM EMP
GROUP BY DEPTNO
HAVING COUNT(DEPTNO)>3;

SELECT CUSTID,COUNT(ORDID) AS [ARITHMOS PARAGERLIWN]
FROM ORD
GROUP BY CUSTID
HAVING COUNT(ORDID)>3;

SELECT ORDID,SUM(QTY) AS [SYNOLIKH POSOTHTA]
FROM ITEM
WHERE ITEMID<=5
GROUP BY ORDID;

SELECT PRODID,AVG(ACTUALPRICE) AS [MESH TIMH]
FROM ITEM
WHERE ORDID=615 OR ORDID<608
GROUP BY PRODID;