Oracle PLSQL之HAVING后面的条件可由聚合函数构成，也可由GROUP BY后的字段构成

HAVING主要用于对分组后的数据进行过滤，

一般我们在其后接聚合函数（SUM，COUNT等），

除此之外我们还可以用GROUP BY后面的字段组成HAVING后的过滤条件。

SQL> select * from dept; DEPTNO DNAME LOC ------ -------------- ------------- 10 ACCOUNTING NEW YORK 20 RESEARCH DALLAS 30 SALES CHICAGO 40 OPERATIONS BOSTON 50 name1 loc1 51 name1 name1 52 loc1 loc1 7 rows selected SQL> SELECT loc FROM dept GROUP BY loc HAVING count(deptno)>1; LOC ------------- loc1 SQL> SELECT loc FROM dept GROUP BY loc HAVING deptno>30; SELECT loc FROM dept GROUP BY loc HAVING deptno>30 ORA-00979: not a GROUP BY expression SQL> SELECT loc FROM dept GROUP BY loc,deptno HAVING deptno>30; LOC ------------- BOSTON loc1 loc1 name1 SQL> SELECT loc,deptno FROM dept GROUP BY loc,deptno HAVING deptno>30; LOC DEPTNO ------------- ------ BOSTON 40 loc1 50 loc1 52 name1 51 SQL>