SQLD(SQL 개발자) 기출 · 집계 함수

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1. 1.SELECT
   COUNT(CASE WHEN CLASS ='A' THEN 1 END) AS "Result"
   COUNT(CASE WHEN CLASS ='B' THEN 1 END) AS B,
   COUNT(CASE WHEN CLASS ='C' THEN 1 END) AS C
   FROM Mytest;
2. 2.SELECT CLASS,
   count(1) AS "Result"
   FROM Mytest
   GROUP BY CLASS;
3. 3.SELECT CLASS,
   count(distinct NAME) AS "Result"
   FROM mytest
   GROUP BY CLASS;
4. 4.SELECT CLASS,
   count(*) AS "Result"
   FROM Mytest
   GROUP BY CLASS;