sql 在案例中使用聚合函数进行查询

Question

我正在尝试解决 http://www.sqlzoo.net/wiki/The_JOIN_operation

上的 #13

"List every match with the goals scored by each team as shown. This will use "CASE WHEN”，这在之前的任何练习中都没有解释过。”

这是我写的：

select distinct mdate, team1,
 case 
    when teamid = team1
      count(teamid)
 end as score1, team2,
 case 
    when teamid = team2
     count(teamid) 
 end as score2
from game join goal on id = matchid
group by matchid
order by mdate, matchid, team1, team2;

我收到这个错误：

You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'count(teamid) end as score1, team2, case when teamid = tea' at line 4

我的代码有什么问题？

Answer 1

你在案例条件和使用函数方面走错了路..下面的查询给你结果..检查并学习希望它会有所帮助

SELECT  game.mdate, 
        game.team1,
        SUM(CASE WHEN goal.teamid=game.team1 THEN 1 ELSE 0 END) score1, 
        game.team2,
        SUM(CASE WHEN goal.teamid=game.team2 THEN 1 ELSE 0 END) score2
FROM game
INNER JOIN goal 
    ON game.id=goal.matchid
GROUP BY game.mdate, goal.matchid, game.team1, game.team2

sql 在案例中使用聚合函数进行查询

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