인구통계 그룹별 금메달
(서유럽 국가만)
+----------+--------------------+-------+
| season | demographic_group | golds |
|----------+--------------------+-------|
| Winter | Male Age 26+ | 13 |
| Winter | Female Age 26+ | 8 |
| Summer | Male Age 13-25 | 7 |
| Summer | Female Age 13-25 | 6 |
| Winter | Male Age 13-25 | 4 |
| Summer | Male Age 26+ | 4 |
| Winter | Female Age 13-25 | 4 |
| Summer | Female Age 26+ | 2 |
+----------+--------------------+-------+
관련 테이블
관련 테이블
옵션 A: 먼저 JOIN, 다음 UNION
옵션 A: 먼저 JOIN, 다음 UNION
1단계: 상단 쿼리를 JOIN으로 설정
SELECT
athlete_id,
gender,
age,
gold
FROM summer_games AS sg
JOIN athletes AS a
ON sg.athlete_id = a.id;
쿼리가 성공적으로 실행되었습니다!
옵션 A: 먼저 JOIN, 다음 UNION
2단계: 하단 쿼리 작성 + 두 {{1}}를 UNION
SELECT
athlete_id,
gender,
age,
gold
FROM summer_games AS sg
JOIN athletes AS a
ON sg.athlete_id = a.id
UNION ALL
SELECT
athlete_id,
gender,
age,
gold
FROM winter_games AS wg
JOIN athletes AS a
ON wg.athlete_id = a.id;
옵션 B: 먼저 UNION, 다음 JOIN
옵션 B: 먼저 UNION, 다음 JOIN
1단계: 초기 UNION 생성
SELECT
athlete_id,
gold
FROM summer_games AS sg
UNION
SELECT
athlete_id,
gold
FROM winter_games AS wg;
옵션 B: 먼저 UNION, 다음 JOIN
2단계: 서브쿼리로 변환 + JOIN
SELECT
athlete_id,
gender,
age,
gold
FROM
(SELECT
athlete_id,
gold
FROM summer_games AS sg
UNION ALL
SELECT athlete_id, gold
FROM winter_games AS wg) AS g
JOIN athletes AS a
ON g.athlete_id = a.id;
비교
옵션 A
SELECT
athlete_id,
gender,
age,
gold
FROM summer_games AS sg
JOIN athletes AS a
ON sg.athlete_id = a.id
UNION ALL
SELECT
athlete_id,
gender,
age,
gold
FROM winter_games AS wg
JOIN athletes AS a
ON wg.athlete_id = a.id;
옵션 B
SELECT
athlete_id,
gender,
age,
gold
FROM
(SELECT
athlete_id,
gold
FROM summer_games AS sg
UNION ALL
SELECT athlete_id, gold
FROM winter_games AS wg) AS g
JOIN athletes AS a
ON g.athlete_id = a.id;
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