我正在写一个曲棍球统计数据库。我有必要计算在进球时有多少球员在冰上。
我已经设置了以下sqlfiddle： http://sqlfiddle.com/#!9/ed8fa
我遇到的问题是如何过滤结果，以便只有在常规力量下得分的目标（击球类型“reg”）或在得分短缺时得分的目标（击球类型“sh”）计入此总数。
我需要在输出中列出所有玩家，即使他们的数字为零。在找到球员“加上评级”后，我将计算每个球员的“减去评分”并减去两个。一旦我弄清楚如何准确地找到“加上评级”，我应该能够弄清楚如何做其余的事情。
对于sqlfiddle中的给定数据，所需的输出应为：
player_id Plus_count
20 1
21 0
22 2
23 1
24 1
25 0
26 1
27 1
28 1
29 0
30 0
31 2
32 1
33 0
我无法弄清楚联接是如何工作的，这样我就可以在哪里过滤掉所有“pp”的目标。
感谢您提供的任何指示......
添加我尝试过的内容。这是来自我的dev db，所以与sqlfiddle略有不同：
SELECT players.player_id as pp_id,
COALESCE(plus_players.count, 0) as Plus_Count
FROM players
LEFT JOIN (SELECT plus_players.fk_player_id, COUNT(*) as count
FROM plus_players
GROUP BY plus_players.fk_player_id) plus_players
ON plus_players.fk_player_id = players.player_id
left join (select * from shots_for
where regular_powerplay_shorthanded = 'reg' or regular_powerplay_shorthanded = 'sh') sf on sf.fk_player_id = players.player_id
union
SELECT players.player_id as pp_id,
COALESCE(plus_players.count, 0) as Plus_Count
FROM players
LEFT JOIN (SELECT plus_players.fk_player_id, COUNT(*) as count
FROM plus_players
GROUP BY plus_players.fk_player_id) plus_players
ON plus_players.fk_player_id = players.player_id
right join (select * from shots_for
where regular_powerplay_shorthanded = 'reg' or regular_powerplay_shorthanded = 'sh') sf2 on sf2.fk_player_id = players.player_id
left join goals_for on goals_for.fk_shot_for_id = sf2.shot_for_id
where regular_powerplay_shorthanded = 'reg' or regular_powerplay_shorthanded = 'sh'
你可以看到我上面的各种尝试，用它来消除“pp”目标。