설치·접속: PostgreSQL 설치와 접속부제: 학생 성적(또는 고객 결제액)을 사분위(4등분)로 나눠 "상위 25%"를 라벨링할 때SELECT student_id, score, ntile(4) OVER w AS quartile, round(percent_rank() OVER w::numeric, 3) AS pct_rank, round(cume_dist() OVER w::numeric, 3) AS cume_distFROM scoresWINDOW w AS (ORDER BY score)ORDER BY score; student_id | score | quartile | pct_rank | cume_dist ----..