MySQL：获取满足特定条件增量的项目数

考虑一张显示各种水果及其数量的表格：

x---------x-----x    
| FRUIT   | QTY |      
x---------x-----x
| Apple   |  4  |
| Orange  |  5  |
| Mango   |  4  |
| Grape   |  1  |
| Plum    |  2  |
| Peach   |  2  |
x---------x-----x

从这个表中，我想查询水果的数量，即计算从0开始到MaxQuaty结束的特定数量的记录的数量，这样我的结果集将是：

x-----x-------x    
| QTY | COUNT |      
x-----x-------x
|  0  |   0   |   //0 fruits have 0 quantity
|  1  |   1   |   //1 fruit (Grape) has 1 quantity
|  2  |   2   |   //2 fruits (Plum, Peach) have 2 quantity
|  3  |   0   |   //0 fruits have 3 quantity
|  4  |   2   |   //2 fruits (Apple, Mango) have 4 quantity
|  5  |   1   |   //1 fruit (Orange) has 5 quantity
x-----x-------x

---

如何实现这一点？

您需要有一个序列表，以便可以与该表进行左连接并给出所有值

这里有一种方法可以做到这一点

数字的生成取自此帖子

试试这个：

Declare @sSQL as Varchar(1000), @sTemp as Varchar(4)
Declare @iLoop as int, @iMax as int
Set @iMax = (Select max(Qty) from table1)
Set @iLoop = 0
Set @sSQL = ''
While @iLoop <= @iMax
Begin
    Set @sTemp = (Select count(Qty) from table1 Where Qty = @iLoop Group By Qty)
    If @sTemp is Null
    Begin
        Set @sTemp = 0
    End
    Set @sSQL = @sSQL + ' Select  '+Cast(@iLoop as Varchar(4))+' as QTY,' + @sTemp+' as [COUNT] Union'

    Set @iLoop = @iLoop + 1
End
Set @sSQL = Left(@sSQL, Len(@sSQL)-5)
Exec(@sSQL)

select * from (select QTY,count(FRUIT) as Count,group_concat(FRUIT) as Fruit_Name from table group by QTY )t Order By QTY

Declare @sSQL as Varchar(1000), @sTemp as Varchar(4)
Declare @iLoop as int, @iMax as int
Set @iMax = (Select max(Qty) from table1)
Set @iLoop = 0
Set @sSQL = ''
While @iLoop <= @iMax
Begin
    Set @sTemp = (Select count(Qty) from table1 Where Qty = @iLoop Group By Qty)
    If @sTemp is Null
    Begin
        Set @sTemp = 0
    End
    Set @sSQL = @sSQL + ' Select  '+Cast(@iLoop as Varchar(4))+' as QTY,' + @sTemp+' as [COUNT] Union'

    Set @iLoop = @iLoop + 1
End
Set @sSQL = Left(@sSQL, Len(@sSQL)-5)
Exec(@sSQL)