如何从SQL Server中的表中检索具有两列唯一值的唯一记录

Question

我想查询一个表，其中我需要包含两列唯一值的结果。对于例如

表

EnquiryId  |  EquipmentId | Price
-----------+--------------+-------
    1      |       E20    |  10
    1      |       E50    |  40
    1      |       E60    |  20   
    2      |       E30    |  90
    2      |       E20    |  10
    2      |       E90    |  10
    3      |       E90    |  10
    3      |       E60    |  10

每个EnquiryId, EquipmentId在表格中都是唯一的。现在我想要一个结果，我可以得到这样的东西

  EnquiryId  |  EquipmentId | Price
  -----------+--------------+-------
    1        |     E20      |  10        
    2        |     E30      |  90        
    3        |     E90      |  10

在结果中，表中存在的每个enquiryId都应该唯一显示。

如果假设我有3 EquipmentIds＆＃34; E20，E50，E60＆＃34;对于EnquiryId＆＃34; 1＆＃34; ..只应从这三个值中显示任意随机EquipmentId。

任何帮助将不胜感激。提前谢谢。

Answer 1

<强> QUERY

;WITH cte AS
(
    SELECT *,
    ROW_NUMBER() OVER 
   (PARTITION BY enquiryID 
    ORDER BY enquiryID ) AS RN
    FROM tbl
)
SELECT enquiryID,equipmentID,Price
FROM cte     
WHERE RN=1

的 FIND FIDDLE HERE

Answer 2

以下代码必须帮助您.. 对不起，我最终只是在一个冗长的解决方案。在SSMS中运行它并查看结果。

Declare @tab table (EnquiryId int,  EquipmentId varchar(10),Price int)
Insert into @tab values

    (1,'E20',10),
    (1,'E50',40),
    (1,'E60',20),   
    (2,'E30',90),
    (2,'E20',10),
    (2,'E90',10),
    (3,'E90',10),
    (3,'E60',10)
----------------------------------------------
Declare @s int = 1
Declare @e int,@z varchar(10)

Declare @Equipment table (EquipmentId varchar(10),ind int)
Insert into @Equipment (EquipmentId) Select Distinct EquipmentId From @tab

Declare @Enquiry table (id int identity(1,1),EnquiryId int,EquipmentId varchar(10))
Insert into @Enquiry (EnquiryId) Select Distinct EnquiryId From @tab

Set @e = @@ROWCOUNT

While @s <= @e
begin
    Select  Top 1 @z = T.EquipmentId
    From    @tab T
    Join    @Enquiry E On T.EnquiryId = E.EnquiryId
    Join    @Equipment Eq On Eq.EquipmentId = T.EquipmentId
    Where   E.id = @s
    And     Eq.ind is Null
    Order by NEWID()

    update  @Enquiry
    Set     EquipmentId = @z
    Where   id = @s

    update  @Equipment
    Set     ind = 1
    Where   EquipmentId = @z

Set @s = @s + 1
End

Select  T.EnquiryId,T.EquipmentId,T.Price
From    @tab T
left join @Enquiry E on T.EnquiryId = E.EnquiryId
Where   T.EquipmentId = E.EquipmentId

Answer 3

您可以使用GROUP BY（典型方式）删除重复值。

基本步骤是：

1. 改变表＆amp;添加标识列。
2. 按列分组，可以重复。
3. 删除那些记录。

点击此处Remove Duplicate Rows from a Table in SQL Server