Three Solutions to Puzzle of the Week #14

Puzzle of the Week #14:

For each department, find its share in the company’s total payroll. The puzzle should be solved with a single SELECT statement that does not utilize sub-queries, WITH clause, in-line views, temporary tables or PL/SQL functions

Expected Result:

DEPTNO   Share, %
------ ----------
    10      30.15
    20      37.47
    30      32.39

Solutions

#1: Using Analytic Functions (SUM)

SELECT DISTINCT deptno, 
                ROUND(100*SUM(sal)OVER(PARTITION BY deptno)/SUM(sal)OVER(),2) AS "Share, %"
FROM emp
ORDER BY 1
/

DEPTNO   Share, %
------ ----------
    10      30.15
    20      37.47
    30      32.39

#2: Using Cartesian Product

SELECT a.deptno, 
       ROUND(100*SUM(a.sal)*COUNT(DISTINCT a.ROWID)/(SUM(b.sal)*COUNT(DISTINCT b.ROWID)), 2) AS "Share, %"
FROM emp a, emp b
GROUP BY a.deptno
ORDER BY 1
/
DEPTNO   Share, %
------ ----------
    10      30.15
    20      37.47
    30      32.39

#3: Using SUM(DISTINCT ..) on a Cartesian Product

SELECT a.deptno,
       ROUND(100*TRUNC(SUM(DISTINCT a.sal+a.empno/1000000)) /
                 TRUNC(SUM(DISTINCT b.sal+b.empno/1000000)), 2) "Share, %"
FROM emp a, emp b
GROUP BY a.deptno
ORDER BY 1;
DEPTNO   Share, %
------ ----------
    10      30.15
    20      37.47
    30      32.39

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