计算客户之间共享的订单数量

Question

我有一个有两列的表

Order | CustomerID

 1. A | C1 
 2. B | C1 
 3. C | C1 
 4. D | C2 
 5. B | C3 
 6. C | C3
 7. D | C4

它是一张很长的桌子.我想要一个显示的输出

C1 | C3 | 2  #Customer C1 and Customer C3 share 2 orders (i.e. orders, B & C) 
C1 | C2 | 0   #Customer C1 and Customer C2 share 0 orders 
C2 | C4 | 1   #Customer C2 and Customer C4 share 1 orders (i.e. order, D)
C2 | C3 | 0  Customer C2 and Customer C3 share 0 orders  

Answer 1

select 
    a.CustomerId
  , b.CustomerId
  , sum(case when a.[Order] = b.[Order] then 1 else 0 end) as SharedOrders
from t as a
  inner join t as b
    on a.CustomerId < b.CustomerId
group by a.CustomerId, b.CustomerId

测试设置:http://rextester.com/ISSCL35174

收益:

+------------+------------+--------------+
| CustomerId | CustomerId | SharedOrders |
+------------+------------+--------------+
| C1         | C2         |            0 |
| C1         | C3         |            2 |
| C2         | C3         |            0 |
| C1         | C4         |            0 |
| C2         | C4         |            1 |
| C3         | C4         |            0 |
+------------+------------+--------------+

要返回共享订单:

select a.CustomerId
     , b.CustomerId
     , count(*) as SharedOrders
from t as a
  inner join t as b
    on a.CustomerId < b.CustomerId
   and a.[Order] = b.[Order]
group by a.CustomerId, b.CustomerId

收益:

+------------+------------+--------------+
| CustomerId | CustomerId | SharedOrders |
+------------+------------+--------------+
| C1         | C3         |            2 |
| C2         | C4         |            1 |
+------------+------------+--------------+