SQL 查询排序和获取唯一计数

Question

我有一个 table，其中包含以下详细信息

Customer	Deal	DealStage
A	D1	Lost
A	D2	Won
A	D3	Contacted
B	D4	Conatcted
B	D5	Lost
C	D6	Lost
D	D7	Lost

我必须开发一个查询，我应该在其中为每个客户获取唯一的最高阶段。阶段优先级为赢得 > 联系 > 失败。例如，A 有三笔交易，分别是 Won、Lost 和 Contacted。所以我应该考虑赢。同样联系 B 和丢失 C 和 D

是否有可能得到像

这样的输出

Customer	Highets Stage
A	Won
B	Contacted
C	Lost
D	Lost

通过这个，我可以生成一个看起来像

的枢轴table

Stage	CustomerCount
Won	1
Contacted	1
Lost	2

提前致谢

Answer 1

使用windows函数如下：

select * from
(select t.*, 
        row_number() over (partition by customer 
                           order by case when dealstage = 'Won' then 1 
                                         when dealstage = 'Contacted' then 2
                                         when dealstage = 'Lost' then 3 
                                    end
        ) as rn
   from your_table t)
 where rn = 1;

Answer 2

一个选项使用聚合和 field():

select customer,
    case min(field(deal_stage, 'Won', 'Contacted', 'Lost'))
        when 1 then 'Won'
        when 2 then 'Contacted'
        when 3 then 'Lost'
    end as highest_stage
from mytable
group by customer

实际上我们可以将它与 elt():

结合起来

select customer,
    elt(
        min(field(deal_stage, 'Won', 'Contacted', 'Lost')), 
        'Won', 'Contacted', 'Lost'
    ) as highest_stage
from mytable
group by customer

然后您可以使用另一个聚合级别生成最终结果：

select highest_stage, count(*)
from (
    select customer,
        elt(
            min(field(deal_stage, 'Won', 'Contacted', 'Lost')), 
            'Won', 'Contacted', 'Lost'
        ) as highest_stage
    from mytable
    group by customer
) t
group by highest_stage

Answer 3

这实际上是两个不同的问题。事实上，我会推荐两种不同的方法。首先，条件聚合：

select customer, 
       coalesce(max(case when state = 'Won' then state end),
                max(case when state = 'Contacted' then state end),
                max(case when state = 'Lost' then state end)
               ) as biggest_state                
from t
group by customer;

但是，对于您的最终结果，我建议使用相关子查询：

select t.state, count(*)
from t
where t.state = (select t2.state
                 from t2
                 where t2.customer = t.customer
                 order by field(state, 'Won', 'Contact', 'Lost')
                 limit 1
                )
group by t.state;

注意：这里假定原始数据没有重复行。如果是，那么 count(distinct) 是一个调整。

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