-- 197_study_questions_exam_round_idx.sql (3/3)
-- 회차별 진행률 (max + count) 조회 고속화.
-- partial — 회차 미설정 / soft-deleted 행 제외해서 인덱스 부피 절약.
-- GET /api/study-topics/{id}/exam-rounds 의 GROUP BY exam_round 가 본 인덱스 활용.

CREATE INDEX IF NOT EXISTS idx_study_questions_topic_round_qnum
    ON study_questions (study_topic_id, exam_round, exam_question_number)
    WHERE deleted_at IS NULL AND exam_round IS NOT NULL;