MySQL SELECT从多个表，多个GROUP BY和group_concat? [英] MySQL SELECT from multiple tables, multiple GROUP BY and group_concat?

问题描述

我有三个要在MySQ中查询的表.如下:

I have three tables which I want to query in MySQ. As follows:

**Table: Leaderboard**
Name  | Score
------------
James | 1
Steve | 2
Dave  | 5

**Table: Actions**
Name  | Action       | Time
----------------------------
James | Ate an apple | 01:00
James | Kicked a dog | 02:00
Steve | Ate a dog    | 03:00
Steve | Kicked a hen | 01:00
Dave  | died         | 02:00

**Table: Items**
Name  | Item         | Time
----------------------------
James | Chainsaw     | 01:00
James | Hammer       | 01:05
James | Crowbar      | 01:10
Steve | Hammer       | 02:00
Steve | Egg          | 01:05
Dave  | Egg          | 01:05

我需要一个查询来选择每个玩家(按Leaderboard.score DESC排序)并选择他们最新的Action WHERE Actions.action LIKE'Ate％'，然后给出所有Items.Item ORDER BY Time DESC

I need a query which selects each player (ORDER BY Leaderboard.score DESC) and selects their latest Action WHERE Actions.action LIKE 'Ate %', and then gives all Items.Item ORDER BY Time DESC

例如，输出看起来像这样

So for example, the output would look like this

**Output**
Name   | Latest_Action | Items
Steve  | Ate a dog     | Hammer, Egg
James  | Ate an apple  | Crowbar, Hammer, Chainsaw

到目前为止，我已经尝试了以下查询，但是它在group_concat中多次返回了每个项目

So far I have tried the following query but it returns each Item multiple times in the group_concat

SELECT Leaderboard.Name, Actions.*, group_concat(Items.Item)
FROM Leaderboard, Actions, Items
WHERE Items.Name = Actions.Name
  AND Actions.Action LIKE 'Ate %'
  AND Actions.Name IN (SELECT Name FROM Leaderboard ORDER BY SCORE DESC)
GROUP BY Leaderboard.name

任何帮助，不胜感激！

推荐答案

SELECT Leaderboard.Name,
  (SELECT Actions.Action
   FROM Actions
   WHERE Actions.Name = Leaderboard.Name
     AND Actions.Action LIKE 'Ate%'
   ORDER BY Time DESC
   LIMIT 1
  ) AS Latest_Action,
  GROUP_CONCAT(Items.Item
               ORDER BY Items.Time DESC
               SEPARATOR ', '
              ) AS Items
FROM Leaderboard
     LEFT JOIN Items ON Leaderboard.Name = Items.Name
GROUP BY Leaderboard.Name
HAVING Latest_Action IS NOT NULL
ORDER BY Leaderboard.Score DESC

在 SQL小提琴中验证的结果.

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