Oracle 21c

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CREATE TABLE DEPT
       (DEPTNO NUMBER(2) PRIMARY KEY,
        DNAME VARCHAR2(14),
        LOC VARCHAR2(13) );
CREATE TABLE EMP
       (EMPNO NUMBER(4) PRIMARY KEY,
        ENAME VARCHAR2(10),
        JOB VARCHAR2(9),
        MGR NUMBER(4) REFERENCES EMP,
        HIREDATE DATE,
        SAL NUMBER(7, 2),
        COMM NUMBER(7, 2),
        DEPTNO NUMBER(2) REFERENCES DEPT);
BEGIN
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');

INSERT INTO EMP VALUES
        (7839, 'KING',   'PRESIDENT', NULL,
        TO_DATE('17-MAR-1981', 'DD-MON-YYYY'), 5000, NULL, 10);
INSERT INTO EMP VALUES
        (7566, 'JONES',  'MANAGER',   7839,
        TO_DATE('2-MAR-1981', 'DD-MON-YYYY'),  2975, NULL, 20);
INSERT INTO EMP VALUES
        (7698, 'BLAKE',  'MANAGER',   7839,
        TO_DATE('1-MAR-1981', 'DD-MON-YYYY'),  2850, NULL, 30);
INSERT INTO EMP VALUES
        (7782, 'CLARK',  'MANAGER',   7839,
        TO_DATE('9-MAR-1981', 'DD-MON-YYYY'),  2450, NULL, 10);        

INSERT INTO EMP VALUES
        (7499, 'ALLEN',  'SALESMAN',  7698,
        TO_DATE('20-MAR-1981', 'DD-MON-YYYY'), 1600,  300, 30);
INSERT INTO EMP VALUES
        (7521, 'WARD',   'SALESMAN',  7698,
        TO_DATE('22-MAR-1981', 'DD-MON-YYYY'), 1250,  500, 30);

INSERT INTO EMP VALUES
        (7654, 'MARTIN', 'SALESMAN',  7698,
        TO_DATE('28-MAR-1981', 'DD-MON-YYYY'), 1250, 1400, 30);

INSERT INTO EMP VALUES
        (7788, 'SCOTT',  'ANALYST',   7566,
        TO_DATE('09-MAR-1982', 'DD-MON-YYYY'), 3000, NULL, 20);
INSERT INTO EMP VALUES
        (7844, 'TURNER', 'SALESMAN',  7698,
        TO_DATE('8-MAR-1981', 'DD-MON-YYYY'),  1500,    0, 30);
INSERT INTO EMP VALUES
        (7876, 'ADAMS',  'CLERK',     7788,
        TO_DATE('12-MAR-1983', 'DD-MON-YYYY'), 1100, NULL, 20);
INSERT INTO EMP VALUES
        (7900, 'JAMES',  'CLERK',     7698,
        TO_DATE('3-MAR-1981', 'DD-MON-YYYY'),   950, NULL, 30);
INSERT INTO EMP VALUES
        (7902, 'FORD',   'ANALYST',   7566,
        TO_DATE('3-MAR-1981', 'DD-MON-YYYY'),  3000, NULL, 20);
INSERT INTO EMP VALUES
        (7369, 'SMITH',  'CLERK',     7902,
        TO_DATE('17-MAR-1980', 'DD-MON-YYYY'),  800, NULL, 20);
INSERT INTO EMP VALUES
        (7934, 'MILLER', 'CLERK',     7782,
        TO_DATE('23-MAR-1982', 'DD-MON-YYYY'), 1300, NULL, 10);
END;
/
1 rows affected

SELECT 'Most earned: '||TO_CHAR(MAX(avg_sal), 'fm99999990.00')
       ||' in '||LISTAGG(CASE avg_sal_rank_desc WHEN 1 THEN dname END, ',')
                   WITHIN GROUP (ORDER BY dname)
       ||', Least earned: '||TO_CHAR(MIN(avg_sal), 'fm99999990.00')
       ||' in '||LISTAGG(CASE avg_sal_rank_asc WHEN 1 THEN dname END, ',')
                   WITHIN GROUP (ORDER BY dname)
       ||', Difference: '||TO_CHAR(MAX(avg_sal)-MIN(avg_sal), 'fm99999990.00')
         AS average_salary_details
FROM   (
  SELECT d.deptno,
         MAX(d.dname) AS dname,
         COALESCE(AVG(e.sal), 0) AS avg_sal,
         RANK() OVER (ORDER BY COALESCE(AVG(e.sal), 0) ASC) AS avg_sal_rank_asc,
         RANK() OVER (ORDER BY COALESCE(AVG(e.sal), 0) DESC) AS avg_sal_rank_desc
  FROM   dept d
         LEFT OUTER JOIN emp e
         ON (d.deptno = e.deptno)
  GROUP BY d.deptno
)
WHERE  avg_sal_rank_asc = 1
OR     avg_sal_rank_desc = 1


AVERAGE_SALARY_DETAILS


Most earned: 2916.67 in ACCOUNTING, Least earned: 0.00 in OPERATIONS, Difference: 2916.67


SELECT 'Most earned: '||TO_CHAR(MAX(avg_sal), 'fm99999990.00')
       ||' in '||LISTAGG(CASE avg_sal_rank_desc WHEN 1 THEN dname END, ',')
                   WITHIN GROUP (ORDER BY dname)
       ||', Least earned: '||TO_CHAR(MIN(avg_sal), 'fm99999990.00')
       ||' in '||LISTAGG(CASE avg_sal_rank_asc WHEN 1 THEN dname END, ',')
                   WITHIN GROUP (ORDER BY dname)
       ||', Difference: '||TO_CHAR(MAX(avg_sal)-MIN(avg_sal), 'fm99999990.00')
         AS average_salary_details
FROM   (
  SELECT d.deptno,
         MAX(d.dname) AS dname,
         COALESCE(AVG(e.sal), 0) AS avg_sal,
         RANK() OVER (ORDER BY COALESCE(AVG(e.sal), 0) ASC) AS avg_sal_rank_asc,
         RANK() OVER (ORDER BY COALESCE(AVG(e.sal), 0) DESC) AS avg_sal_rank_desc
  FROM   dept d
         INNER JOIN emp e
         ON (d.deptno = e.deptno)
  GROUP BY d.deptno
)
WHERE  avg_sal_rank_asc = 1
OR     avg_sal_rank_desc = 1


AVERAGE_SALARY_DETAILS


Most earned: 2916.67 in ACCOUNTING, Least earned: 1566.67 in SALES, Difference: 1350.00