自然连接多个表后如何使用 Group By

Question

这是一道作业题。

我有一个团队：

teamid | teamcity | name

桌游：

gameid | date | gamecity

还有一个玩过的桌面游戏

gameid | teamid | teamscore

我想要做的是只选择两支球队所在城市都不是比赛所在城市的比赛。

例如，如果多伦多猛龙队和芝加哥公牛队在纽约打了一场比赛，那将会被选中。

我尝试了几种不同的方法，包括：

WITH TEMP as (SELECT * FROM GAME NATURAL JOIN 
GAME_PLAYED NATURAL JOIN TEAM WHERE teamcity != gamecity) 
SELECT gameid, gamecity, teamcity, teamname, teamscore FROM TEMP GROUP BY 
gameid, gameid HAVING COUNT(gameid) > 1;

和：

SELECT gameid, gamecity, teamcity, teamname, teamscore FROM GAME 
NATURAL JOIN GAME_PLAYED NATURAL JOIN TEAM WHERE teamcity != gamecity
GROUP BY gameid HAVING COUNT(gameid) > 1;

我不确定从这里去哪里。最后一个给我一个错误：“列“teams.teamcity”必须出现在 GROUP BY 子句中或用于聚合函数中”。

Answer 1

我想通了：

SELECT gameid, gamecity, teamcity, teamname, teamscore FROM GAME_PLAYED 
NATURAL JOIN GAME NATURAL JOIN TEAM WHERE gameid IN
(SELECT gameid FROM GAME NATURAL JOIN GAME_PLAYED NATURAL JOIN TEAM 
WHERE teamcity != gamecity GROUP BY gameid, gameid HAVING COUNT(gameid) 
> 1) ORDER BY gameid;