如何根据运动员在该运动中获胜的奖牌数量，使用以下6个表格返回给定国家和运动的前三名运动员名单？
ATHLETES
+------------+-----------------+---------------+-------------------------+
| idATHLETES | ATHLETENAME | TEAMS_idTEAMS | TEAMS_COUNTRY_idCOUNTRY |
+------------+-----------------+---------------+-------------------------+
| JG | JUSTIN GATLIN | USA-TF-MEN | USA |
| MS | MARIA SHARAPOVA | RUS-WTA | RUS |
| SW | SERENA WILLIAMS | USA-WTA | USA |
| UB | USAIN BOLT | JAM-TF-MEN | JAM |
| VW | VENUS WILLIAMS | USA-WTA | USA |
+------------+-----------------+---------------+-------------------------+
EVENTS
+------------+---------------+---------------------+------------------------+----------------------------------+--------------------------+
| idEVENTS | EVENTNAME | ATHLETES_idATHLETES | ATHLETES_TEAMS_idTEAMS | ATHLETES_TEAMS_COUNTRY_idCOUNTRY | VARIOUS_SPORTS_SPORTS_ID |
+------------+---------------+---------------------+------------------------+----------------------------------+--------------------------+
| ATH | ATHLETICS | JG | USA-TF-MEN | USA | TRACK-AND-FIELD |
| ATH | ATHLETICS | UB | JAM-TF-MEN | JAM | TRACK-AND-FIELD |
| TEN | TENNIS | MS | RUS-WTA | RUS | WOMENS_TENNIS |
| TEN | TENNIS | VW | USA-WTA | USA | WOMENS_TENNIS |
| TEN-DOUBLE | TENNIS DOUBLE | SW | USA-WTA | USA | WOMENS_TENNIS |
| TEN-DOUBLE | TENNIS DOUBLE | VW | USA-WTA | USA | WOMENS_TENNIS |
+------------+---------------+---------------------+------------------------+----------------------------------+--------------------------+
RESULTS
+-----------+-------------+--------+-----------------+----------------------------+-------------------------------+----------------------------------------
+-----------+-------------+--------+-----------------+----------------------------+-------------------------------+-----------------------------------------+---------------------------------+
| idRESULTS | STATUS | MEDALS | EVENTS_idEVENTS | EVENTS_ATHLETES_idATHLETES | EVENTS_ATHLETES_TEAMS_idTEAMS | EVENTS_ATHLETES_TEAMS_COUNTRY_idCOUNTRY | EVENTS_VARIOUS_SPORTS_SPORTS_ID |
+-----------+-------------+--------+-----------------+----------------------------+-------------------------------+-----------------------------------------+---------------------------------+
| results1 | DID-NOT-WIN | SILVER | TEN | MS | RUS-WTA | RUS | WOMENS_TENNIS |
| results1 | WON | GOLD | TEN | VW | USA-WTA | USA | WOMENS_TENNIS |
| results2 | DID-NOT-WIN | BRONZE | ATH | JG | USA-TF-MEN | USA | TRACK-AND-FIELD |
| results2 | WON | GOLD | ATH | UB | JAM-TF-MEN | JAM | TRACK-AND-FIELD |
| results3 | WON | GOLD | TEN-DOUBLE | SW | USA-WTA | USA | WOMENS_TENNIS |
| results3 | WON | GOLD | TEN-DOUBLE | VW | USA-WTA | USA | WOMENS_TENNIS |
+-----------+-------------+--------+-----------------+----------------------------+-------------------------------+-----------------------------------------+---------------------------------+
VARIOUS_SPORTS
+-----------------+----------------------+
| SPORTS_ID | SPORTS_NAME |
+-----------------+----------------------+
| TRACK-AND-FIELD | MENS TRACK AND FIELD |
| WOMENS_TENNIS | WOMENS TENNIS |
+-----------------+----------------------+
THE_COUNTRY
+-----------+-------------+
| idCOUNTRY | COUNTRYNAME |
+-----------+-------------+
| JAM | JAMAICA |
| RUS | RUSSIA |
| USA | USA |
+-----------+-------------+
THE_TEAMS
+------------+----------------------------------+-------------------+
| idTEAMS | TEAMNAME | COUNTRY_idCOUNTRY |
+------------+----------------------------------+-------------------+
| JAM-TF-MEN | jamaican track and field men | JAM |
| RUS-WTA | russian women tennis association | RUS |
| USA-TF-MEN | usa track and field men | USA |
| USA-WTA | usa womens tennis association | USA |
+------------+----------------------------------+-------------------+
到目前为止我有这个代码，但这不会返回所需的输出？
SELECT idATHLETES, ATHLETENAME, TEAMS_COUNTRY_idCOUNTRY, COUNTRYNAME FROM
athletes
JOIN EVENTS ON idATHLETES = idEVENTS
JOIN teams ON TEAMS_idTEAMS =idTEAMS
JOIN country ON COUNTRY_idCOUNTRY = idCOUNTRY
JOIN RESULTS ON ATHLETES_idATHLETES = EVENTS_ATHLETES_idATHLETES
WHERE EVENTS_VARIOUS_SPORTS_SPORTS_ID = 'WOMENS_TENNIS' AND EVENTS_ATHLETES_TEAMS_COUNTRY_idCOUNTRY ='USA' ;
答案 0 :(得分：1)
考虑运动员分组并计算奖牌。
SELECT idATHLETES, ATHLETENAME, TEAMNAME, COUNTRYNAME
, MEDALS = SUM(CASE WHEN MEDALS IS NULL THEN 0 ELSE 1 END)
, SCORE = SUM(CASE MEDALS WHEN 'Gold' THEN 3
WHEN 'Silver' THEN 2
WHEN 'Bronze' THEN 1
ELSE 0 END)
, GOLD = SUM(CASE MEDALS WHEN 'Gold' THEN 1 ELSE 0 END)
, SILVER = SUM(CASE MEDALS WHEN 'Silver' THEN 1 ELSE 0 END)
, BRONZE = SUM(CASE MEDALS WHEN 'Bronze' THEN 1 ELSE 0 END)
FROM ATHLETES
JOIN TEAMS ON TEAMS_idTEAMS = idTEAMS
JOIN COUNTRY ON COUNTRY_idCOUNTRY = idCOUNTRY
JOIN RESULTS ON ATHLETES_idATHLETES = EVENTS_ATHLETES_idATHLETES
WHERE EVENTS_VARIOUS_SPORTS_SPORTS_ID = 'WOMENS_TENNIS'
AND EVENTS_ATHLETES_TEAMS_COUNTRY_idCOUNTRY ='USA'
GROUP BY idATHLETES, ATHLETENAME, TEAMNAME, COUNTRYNAME
ORDER BY SUM(CASE WHEN MEDALS IS NULL THEN 0 ELSE 1 END) DESC
LIMIT 3
如果您需要为每枚奖牌指定不同的点数，您可以将ORDER BY子句更改为：
ORDER BY SUM(CASE MEDALS WHEN 'Gold' THEN 3
WHEN 'Silver' THEN 2
WHEN 'Bronze' THEN 1
ELSE 0 END)
或者，您可以创建一个表来保存值。