sqlにおけるwhere,groupby,havingの使用解析

group by “ ” 。 ： 。 having （group by） ， where     where ， having ， HAVING 。 having     having ， having select 。 ， oracle     where 、group by 、having ， ： where ； group by ； group by ； having
    ex:  ． 1000000 。      SELECT region, SUM(population), SUM(area)      FROM bbc      GROUP BY region      HAVING SUM(area)>1000000      ， where 1000000 ， 。(where )      ，HAVING 1、 20， 2
  select COUNT (age) as '>20 ' ,classid from Table1 where sex=' ' group by classid having COUNT(age)>2  
  *sc( ) 、SNO（ ）、PNO（ ）、GRADE（ ） 2、 90 select sno,pno,grade from sc where grade>=90;
3、 90 // ， where select sno, count (*) from sc where grade>=90 group by sno; 4、 90 90 。
  // ， where ， having 。 90 ， select sno, count (*) from sc where grade>=90 group by sno having count (*)>=2； 5、 90 95 // ， 95 ， ， having 90 select sno,avg(grade) from sc where SNO IN (SELECT SNO FROM SC WHERE GRADE>=95 AND PNO= 'YW' ) group by sno having avg(grade)>=90; 6、 3 //having ， 3 ， ， 。 select sno,avg(grade) from sc group by sno having avg(grade) > (select avg(grade) from sc where sno=3);