选择与自定义联接表成多对多关系的第一行

Question

I have three tables in a MM relationship:

I'm having a lot of trouble trying to figure out how I can retrieve all Bundles with only the first related inventory item ordered by Inventory.Stock ASC but also return the Bundles_Inventory.InventoryRequired field.

I've seen other responses to similar questions but none of them take into account a custom join table.

How can I select all Bundles ordered by Inventory.Stock ASC and also include Bundles_Inventory.InventoryRequired for that record?

In regards to @imran
Originally I had:

SELECT b.Id, b.Name, i.Id, i.Name, i.Stock, bi.InventoryRequired from         Bundles b
INNER JOIN Bundles_Inventory bi ON b.Id = bi.BundleId
INNER JOIN Inventory i ON bi.InventoryId = i.Id
WHERE b.ClientId = @clientId
ORDER BY i.Stock ASC  

But obviously this gets me duplicate data in regards to the Bundles table..

I then tried

SELECT TOP 1 b.Id, b.Name, i.Id, i.Name, i.Stock, bi.InventoryRequired from Bundles b
INNER JOIN Bundles_Inventory bi ON b.Id = bi.BundleId
INNER JOIN Inventory i ON bi.InventoryId = i.Id
WHERE b.ClientId = @clientId
ORDER BY i.Stock ASC  

And right now I'm trying to figure out how I can apply a Group By to figure this out.

Answer 1

You can do this with row_number() in most databases:

select b.*, i.*
from bundles b join
     (select i.*,
             row_number() over (partition by bi.bundleid order by i.stock desc) as seqnum
      from bundles_inventory bi join
           Inventory i 
           on bi.InventoryId = i.Id
     ) i
     on b.id = bi.bundleid 
where seqnum = 1;

You can add the where clause in the outer query.