在 SQLite 中选择每年的最大总和答案

【问题标题】：Select max sum for each year in SQLite在 SQLite 中选择每年的最大总和
【发布时间】：2016-05-20 01:40:05
【问题描述】：

我有一个 SQLite 数据库，用于跟踪有关棋盘游戏的信息（名称、发布年份、机制、发行商、在 www.boardgamegeek.com 上拥有该游戏的人数，以及 boardgamegeek 目前对该游戏的排名）。架构是：

我有兴趣为特定出版商获取每年最受欢迎的机制（拥有最多副本的机制）。我目前的查询是：

select games.year as yr, mechanics.name as mech, sum(collection.owned) as sm
 from games 
 inner join gamemech on games.bggid = gamemech.bggid
 inner join mechanics on gamemech.mechid = mechanics.mechid
 inner join gamepub on gamepub.bggid = games.bggid
 inner join publishers on publishers.pubid = gamepub.pubid
 inner join collection on collection.bggid = games.bggid
 where publishers.name like '%stronghold%'
 group by yr, mech order by yr limit 20;

这会返回：

1974|Commodity Speculation|1460
1974|Dice Rolling|1460
1974|Tile Placement|1460
1982|Action Point Allowance System|16111
1982|Dice Rolling|16111
1982|Modular Board|16111
1982|Secret Unit Deployment|16111
1985|PaperandPencil|1949
1991|Auction/Bidding|1266
1992|Grid Movement|1704
1992|Pickup and Deliver|1704
2011|Action Point Allowance System|7943
2011|Area Control / Area Influence|174
2011|Area Movement|3607
2011|Auction/Bidding|174
2011|Card Drafting|5133
2011|Deck / Pool Building|3768
2011|Dice Rolling|2385
2011|Hand Management|5663
2011|Line Drawing|2141

我真正感兴趣的只是年份、机制以及每年拥有最高金额的机制所拥有的副本总和。像这样（但是可以打破关系）：

1974|Commodity Speculation|1460
1982|Action Point Allowance System|16111
1985|PaperandPencil|1949
1991|Auction/Bidding|1266
1992|Grid Movement|1704
2011|Action Point Allowance System|7943

我想我可能需要在查询中使用另一个 select 语句，但我似乎无法让它工作。有什么建议吗？

【问题讨论】：

标签： sql sqlite select

【解决方案1】：

解决方案刚刚击中我。如果你发现自己在这里，我就是这样做的：

我基本上想得到每个组的 max(sum())。您需要做的第一件事是找出包含所有数据的查询（这是我的第一个查询）。对我来说是：

select games.year as yr, mechanics.name as mech, sum(collection.owned) as sm
 from games 
 inner join gamemech on games.bggid = gamemech.bggid
 inner join mechanics on gamemech.mechid = mechanics.mechid
 inner join gamepub on gamepub.bggid = games.bggid
 inner join publishers on publishers.pubid = gamepub.pubid
 inner join collection on collection.bggid = games.bggid
 where publishers.name like '%stronghold%'
 group by yr, mech order by yr limit 20;

这返回的是主要问题。接下来，我们要从中进行选择。我感兴趣：

games.year, mechanics.name, max(sm)

诀窍是第一个查询中的每个表都需要命名（对我来说是 yr、mech 和 sm），以便您以后可以加入它。最后的查询是：

Select games.year, mechanics.name, max(sm) from (
select games.year as yr, mechanics.name as mech, sum(collection.owned) as sm
 from games 
 inner join gamemech on games.bggid = gamemech.bggid
 inner join mechanics on gamemech.mechid = mechanics.mechid
 inner join gamepub on gamepub.bggid = games.bggid
 inner join publishers on publishers.pubid = gamepub.pubid
 inner join collection on collection.bggid = games.bggid
 where publishers.name like '%stronghold%'
 group by yr, mech)
inner join games on games.year = yr
inner join mechanics on mechanics.name = mech
group by yr;

我希望这是有道理的！

【讨论】：