mysql - 复杂的查询 - 很少有包含分组列的表

Question

我有表:

Worker (ID, Name)

Box (ID, Name, ID_Worker)

BoxColor (ID, Name)
BoxSize (ID, Name)

Item(ID, ID_box, ID_BoxColor, ID_BoxSize)

所以我们有工作人员创建元素并将它们放入盒子中。为了我的 secret 工作，我改变了话题，从我的 secret 到 ehm boxes ;)

我正在尝试创建包含列的报告:

Worker.Name | BoxSize.Name | BoxColor(id=0) | BoxColor(id=1) | BoxColor(id=2)

Table Box在其他raports中使用，所以这种表格结构不能改变。

例如我想要得到的是:

分组的 Worker Names 和每个 BoxSize，在列中包含每个 Color 计数。例如:

John | X   | 2 | 4 | 0 |
John | XL  | 5 | 1 | 0 |
John | XXL | 2 | 0 | 0 |
John | S   | 3 | 1 | 0 |
Adam | X   | 5 | 4 | 0 |
Adam | XL  | 1 | 3 | 0 |
Adam | S   | 0 | 1 | 0 |
....

BoxColor 是一张没有太多颜色的表格，因此可以使用不同的子选择对其进行硬编码，例如

(select count(*) from BoxColor where ID = 0)
(select count(*) from BoxColor where ID = 1)
(select count(*) from BoxColor where ID = 2)

我试图做这样的事情，但查询是循环的，它永远不会停止“思考”

select Worker.Name, BoxSize.Name,
 (select count(*) from BoxColor as BoxColor2, Box as Box2, Item as Item2 
   where Box2.ID_Worker = Worker.ID and 
         Item2.ID_Box = Box2.ID and
         Item2.ID_BoxColor = BoxColor2.ID) and
         BoxColor.ID = 0 ) as Red,
 (select count(*) from BoxColor as BoxColor2, Box as Box2, Item as Item2 
   where Box2.ID_Worker = Worker.ID and 
         Item2.ID_Box = Box2.ID and
         Item2.ID_BoxColor = BoxColor2.ID) and
         BoxColor.ID = 1 ) as Green,
 (select count(*) from BoxColor as BoxColor2, Box as Box2, Item as Item2 
   where Box2.ID_Worker = Worker.ID and 
         Item2.ID_Box = Box2.ID and
         Item2.ID_BoxColor = BoxColor2.ID) and
         BoxColor.ID = 2 ) as Blue,
from Worker, BoxSize, Box, Item
where 
    Item.ID_Worker = Worker.ID and
    Item.ID_Box = Box.ID
    Item.ID_BoxSize = BoxSize.ID
group by Worker.Name, BoxSize.Name
having Red > 0, Blue > 0, Green > 0
order by 1, 2

Answer 1

也许是这样的:

SELECT
    Worker.Name,
    BoxSize.Name,
    SUM(CASE WHEN BoxColor.id=0 THEN 1 ELSE 0 END) AS BoxColor_0,
    SUM(CASE WHEN BoxColor.id=1 THEN 1 ELSE 0 END) AS BoxColor_1,
    SUM(CASE WHEN BoxColor.id=2 THEN 1 ELSE 0 END) AS BoxColor_2    
FROM
    Worker
    JOIN Box
        ON Worker.ID=Box.ID_Worker
    JOIN Item
        ON Item.ID_box=Box.ID
    JOIN BoxColor
        ON BoxColor.ID=Item.ID_BoxColor
    JOIN BoxSize
        ON BoxSize.ID=Item.ID_BoxSize
GROUP BY
    Worker.Name,
    BoxSize.Name