Duplicate Emails

SELECT a.email
FROM (
    SELECT email, COUNT(*) AS count_num
    FROM Person
    GROUP BY email
) AS a ## 필수
WHERE a.count_num >= 2
;
SQL
복사

모든 서브쿼리 테이블들은 Alias가 붙어야 한다

group by로 연산된 칼럼을 계산 → having

SELECT email, count(id) as cnt
FROM Person
GROUP BY Email
HAVING COUNT(id) >= 2
;
SQL
복사