programmers : 중복 제거하기

중복 제거하기

 

MYSQL

-- IS NOT NULL
SELECT COUNT(DISTINCT NAME)
FROM ANIMAL_INS 
WHERE NAME IS NOT NULL;


-- SUBQUERY
SELECT COUNT(NAME)
FROM (SELECT DISTINCT NAME FROM ANIMAL_INS) AI;

ORACLE

COUNT는 *가 아니면 NULL을 세지 않는다.

SELECT COUNT(NAME)
FROM (SELECT DISTINCT NAME FROM ANIMAL_INS);