Incorrect use of DISTINCT

Question

I have a form view that displays the ListingID, PropertyID, ListingAgentID, SaleStatusID, EndListDate and AskingPrice from a database in SQL.

I have a DropDownList that displays the LastNames of agents that when selected it returns back the relevent information in the formView corresponding to the selection.

It's working, but the only problem is that each last name in the dropDownList is duplicated as they each have more than one listing. What I need it to do is when selecting one last name from the DropDownList it returns one value in the FormView, while being able to use paging to view different listings from that agent.

The code in the FormView is:

SELECT[ListingID], 
      [PropertyID], 
      [ListingAgentID], 
      [SaleStatusID], 
      [EndListDate], 
      [AskingPrice] 
FROM [Listings]
WHERE ([ListingID] = @ListingID)

The code in the DropDownList is:

SELECT Agents.LastName, 
       Listings.ListingID, 
       Listings.PropertyID, 
       Listings.ListingAgentID,
       Listings.SaleStatusID, 
       Listings.BeginListDate, 
       Listings.EndListDate,
       Listings.AskingPrice 
FROM Agents 
INNER JOIN Listings 
ON  Agents.AgentID = Listings.ListingAgentID

Where ever I try and put a DISTINCT function it returns an error or doesn't work

Thanks

Answer 1

对于下拉列表，您需要的是一个ID作为值和要显示的姓氏。

SELECT DISTINCT Agents.LastName FROM Agents INNER JOIN Listings ON Agents.AgentID = Listings.ListingAgentID