各部門の従業員数を調べる - SQL Oracle

Question

私は2つのテーブルEmpとDeptを持っており、部門名とともに各部門で働く人数を表示しようとしていますが、動作させることはできません。私はこのselect count(ename) as count from emp group by deptno;を試してみましたが、私は取得しています出力はこれです：

COUNT 
---------- 
    6 
    5 
    3 

しかし、私はまた、これらの部門のそれぞれの名前を表示したいです。

EMPT：

CREATE TABLE EMP 
     (EMPNO NUMBER(4) NOT NULL, 
     ENAME VARCHAR2(10), 
     JOB VARCHAR2(9), 
     MGR NUMBER(4), 
     HIREDATE DATE, 
     SAL NUMBER(7, 2), 
     COMM NUMBER(7, 2), 
     DEPTNO NUMBER(2)); 

INSERT INTO EMP VALUES 
     (7369, 'SMITH', 'CLERK',  7902, 
     TO_DATE('17-DEC-1980', 'DD-MON-YYYY'), 800, NULL, 20); 
INSERT INTO EMP VALUES 
     (7499, 'ALLEN', 'SALESMAN', 7698, 
     TO_DATE('20-FEB-1981', 'DD-MON-YYYY'), 1600, 300, 30); 
INSERT INTO EMP VALUES 
     (7521, 'WARD', 'SALESMAN', 7698, 
     TO_DATE('22-FEB-1981', 'DD-MON-YYYY'), 1250, 500, 30); 
INSERT INTO EMP VALUES 
     (7566, 'JONES', 'MANAGER', 7839, 
     TO_DATE('2-APR-1981', 'DD-MON-YYYY'), 2975, NULL, 20); 
INSERT INTO EMP VALUES 
     (7654, 'MARTIN', 'SALESMAN', 7698, 
     TO_DATE('28-SEP-1981', 'DD-MON-YYYY'), 1250, 1400, 30); 
INSERT INTO EMP VALUES 
     (7698, 'BLAKE', 'MANAGER', 7839, 
     TO_DATE('1-MAY-1981', 'DD-MON-YYYY'), 2850, NULL, 30); 
INSERT INTO EMP VALUES 
     (7782, 'CLARK', 'MANAGER', 7839, 
     TO_DATE('9-JUN-1981', 'DD-MON-YYYY'), 2450, NULL, 10); 
INSERT INTO EMP VALUES 
     (7788, 'SCOTT', 'ANALYST', 7566, 
     TO_DATE('09-DEC-1982', 'DD-MON-YYYY'), 3000, NULL, 20); 
INSERT INTO EMP VALUES 
     (7839, 'KING', 'PRESIDENT', NULL, 
     TO_DATE('17-NOV-1981', 'DD-MON-YYYY'), 5000, NULL, 10); 
INSERT INTO EMP VALUES 
     (7844, 'TURNER', 'SALESMAN', 7698, 
     TO_DATE('8-SEP-1981', 'DD-MON-YYYY'), 1500, 0, 30); 
INSERT INTO EMP VALUES 
     (7876, 'ADAMS', 'CLERK',  7788, 
     TO_DATE('12-JAN-1983', 'DD-MON-YYYY'), 1100, NULL, 20); 
INSERT INTO EMP VALUES 
     (7900, 'JAMES', 'CLERK',  7698, 
     TO_DATE('3-DEC-1981', 'DD-MON-YYYY'), 950, NULL, 30); 
INSERT INTO EMP VALUES 
     (7902, 'FORD', 'ANALYST', 7566, 
     TO_DATE('3-DEC-1981', 'DD-MON-YYYY'), 3000, NULL, 20); 
INSERT INTO EMP VALUES 
     (7934, 'MILLER', 'CLERK',  7782, 
     TO_DATE('23-JAN-1982', 'DD-MON-YYYY'), 1300, NULL, 10); 

部門：

CREATE TABLE DEPT 
     (DEPTNO NUMBER(2), 
     DNAME VARCHAR2(14), 
     LOC VARCHAR2(13)); 

INSERT INTO DEPT VALUES (10, 'ACCOUNTING', 'NEW YORK'); 
INSERT INTO DEPT VALUES (20, 'RESEARCH', 'DALLAS'); 
INSERT INTO DEPT VALUES (30, 'SALES',  'CHICAGO'); 
INSERT INTO DEPT VALUES (40, 'OPERATIONS', 'BOSTON'); 

Answer 1

は試してみてください：

select count(*) as count,dept.DNAME 
from emp 
inner join dept on emp.DEPTNO = dept.DEPTNO 
group by dept.DNAME 

Answer 2

select count(e.empno), d.deptno, d.dname 
from emp e, dep d 
where e.DEPTNO = d.DEPTNO 
group by d.deptno, d.dname; 

Answer 3

SELECT d.DEPTNO 
    , d.dname 
    , COUNT(e.ename) AS count 
FROM emp e 
     INNER JOIN dept d ON e.DEPTNO = d.deptno 
GROUP BY d.deptno 
     , d.dname;