SQLD(SQL 개발자) 기출 · 집계 함수

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1. 1.SELECT JOB, NVL(SUM(CASE WHEN DEPTNO = 10 THEN 1 END),0) AS "10번부서원수", NVL(SUM(CASE WHEN DEPTNO = 20 THEN 1 END),0) AS "20번부서원수", NVL(SUM(CASE WHEN DEPTNO = 30 THEN 1 END),0) AS "30번부서원수" FROM EMP GROUP BY JOB;
2. 2.SELECT JOB, SUM(CASE WHEN DEPTNO = 10 THEN 1 ELSE 0 END) AS "10번부서원수", SUM(CASE WHEN DEPTNO = 20 THEN 1 ELSE 0 END) AS "20번부서원수", SUM(CASE WHEN DEPTNO = 30 THEN 1 ELSE 0 END) AS "30번부서원수" FROM EMP GROUP BY JOB;
3. 3.SELECT JOB, COUNT(CASE WHEN DEPTNO = 10 THEN 1 END) AS "10번부서원수", COUNT(CASE WHEN DEPTNO = 20 THEN 1 END) AS "20번부서원수", COUNT(CASE WHEN DEPTNO = 30 THEN 1 END) AS "30번부서원수" FROM EMP GROUP BY JOB;
4. 4.SELECT JOB, COUNT(CASE WHEN DEPTNO = 10 THEN 1 ELSE 0 END) AS "10번부서원수", COUNT(CASE WHEN DEPTNO = 20 THEN 1 ELSE 0 END) AS "20번부서원수", COUNT(CASE WHEN DEPTNO = 30 THEN 1 ELSE 0 END) AS "30번부서원수" FROM EMP GROUP BY JOB;