使用 COUNT，但仅用于特定值

Question

我有一个保存了比赛的表格，我想生成一个表格来显示当前的排名。到目前为止，我的代码如下所示：

SELECT DISTINCT cname, COUNT(cname) AS games, **COUNT(points WHERE points=3) AS wins**, 1, 0, SUM(goalsscored)-SUM(goalsconceded) AS goaldiff, SUM(po$
FROM pmatch
GROUP BY cname
ORDER BY point DESC, goaldiff DESC

我保存了每场比赛的球队在该比赛中获得的分数。所以我只需要计算每场比赛，一支球队获得 3 分的胜场数，1 分的平局数和 0 分的输球数。

但是，COUNT 命令无法正常工作。在粗体部分，你看到我想计算每场比赛球队得到 3 分的情况。我该如何正确地做到这一点？

提前致谢！！

Answer 1

使用CASE 表达式。

查询

SELECT cname, 
COUNT(cname) AS games, 
SUM(CASE points WHEN 3 THEN 1 ELSE 0 END) AS wins,
SUM(CASE points WHEN 1 THEN 1 ELSE 0 END) AS draws,
SUM(CASE points WHEN 0 THEN 1 ELSE 0 END) AS loses,
SUM(goalsscored)-SUM(goalsconceded) AS goaldiff
FROM pmatch
GROUP BY cname
ORDER BY 3 DESC, 6 DESC;

Answer 2

只需使用CASE:

SELECT cname, COUNT(cname) AS games, COUNT(case when points=3 then 1 end) AS wins, 1, 0, SUM(goalsscored)-SUM(goalsconceded) AS goaldiff
FROM pmatch
GROUP BY cname
ORDER BY wins DESC,  -- probably
     goaldiff DESC