两列成一

Question

我正在尝试将两列合并为一列，其中一列具有空值。它看起来像这样：

| Order Number | MOP    | MOP2   |
| 12345        | Cash   |        |
| 12346        | Credit |        |
| 12347        | Visa   | Cash   |
| 12348        | Credit |        |

我正在运行的查询如下所示：

Select  
  ORDER.OrderHistory.OrderNo  
  ,ORDER.OrderHistory.MOP 
  ,ORDER.OrderHistory.MOP2 
From  
  ORDER.OrderHistory

我试图让它看起来像这样：

| Order Number | MOP    | 
| 12345        | Cash   |  
| 12346        | Credit |
| 12347        | Visa   | 
| 12347        | Cash   |
| 12348        | Credit |  

Answer 1

只需将union两列放入数据集中的同一列：

-- This query will return all your data rows
select o.OrderNo
      ,o.MOP
from ORDER.OrderHistory as o

union all

-- And then this one will get all where the MOP2 column is not null
select o.OrderNo  
      ,o.MOP2 
from ORDER.OrderHistory as o
where o.MOP2 is not null