Question

我使用下面的查询显示所有比赛的得分摘要表。桌面游戏有id，mdate，stadium，team1，team2。表格目标有matchid，玩家名称，teamid，gtime，因此它记录每一个目标。

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

我的查询重新丢失了2个案例，其中两个团队得分为0。

请帮助告知我的语法是否合适。

Answer 1

如果特定LEFT JOIN的{{1}}表格中没有行，您应该使用goal，但仍希望game行生成结果行：

game

当没有SELECT mdate, team1, sum(CASE WHEN teamid=team1 THEN 1 ELSE 0 END) as score1, team2, sum(CASE WHEN teamid=team2 THEN 1 ELSE 0 END) as score2 FROM game LEFT JOIN goal ON matchid = id GROUP BY mdate, team1, team2 ORDER BY mdate, matchid, team1, team2要计数时，这会产生NULL而不是0 s，但可以通过用{包裹goal表达式来解决这个问题。 {1}}，如果结果为SUM非常重要。

在SQL中使用SUM（CASE WHEN）时缺少0值

1 个答案: