inner-join

I encountered some odd behavior using C# HastSet with LINQ's Join method that I don't understand. I've simplified what I am doing to help focus on the behavior I am seeing. I have the following: private HashSet<MyClass> _mySet; // module level IEnumerable<ISearchKey> searchKeys; // parameter. // Partial key searches are allowed. private IEqualityComparer<ICoreKey> _coreKeyComparer; // Module level. // Compares instances of MyClass and ISearchKey to determine // if they match. Given that There is a 1-to-many relationship between searchKeys and _mySet. MyClass implements interface IPartialKey

I am trying to find duplicated vendors from a database using several fields from vendor table and vendor_address table. The thing is the more inner join I make the less the query is loosing potential results. While I don't have duplicate in vendor ID I'm look to find potential one that are similar. Here is my query so far: SELECT o.vendor_id ,o.vndr_name_shrt_user ,O.COUNTRY ,O.VENDOR_NAME_SHORT ,B.POSTAL ,B.ADDRESS1 ,SAME_ADDRESS_NB ,SAME_POSTAL_NB ,OC.SAME_SHORT_NAME ,oc.SAME_USER_NUM FROM VENDOR o JOIN vendor_addr B ON o.VENDOR_ID = B.VENDOR_ID INNER JOIN ( SELECT vndr_name_shrt_user, COUNT

giving the next database I need to make several queries, I'm having troubles when I try to: List of all planets showing the soldiers with a captain rank and the number of the battles in each planet. ID_PLANET | PLANET_NAME | CAPTAINS COUNT | BATTLES COUNT SELECT id_planet, planet_name , count(rank) FROM planet INNER JOIN soldier ON planet_id = id_planet WHERE rank = 'Captain'; List of all soldiers who have been ONLY in a war of their own planet. ID_SOLDIER | NAME_SOLDIER SELECT id_soldier, name FROM soldier INNER JOIN planet ON planet_id = id_planet INNER JOIN battle ON id_planet = id_planet

I have a table called Staff which has the following fields: idStaff, Name, Phone, Email, SupervisorId . The SuervisorId is the idStaff of that staff member's supervisor. I want to show the list of all staff members with their basic info (Name, Email etc) as well as the name of their supervisor. So something like this: select idStaff , Name , Email , Phone , (select Name from Staff where idStaff = SupervisorId) as SupervisorName from Staff order by Name ASC The query does not work. I tried joining the two tables but I am confused on how to get the Name from the subquery in the join. select

I have 2 tables. One is items and another is votes for those items. Items table has: |item_id|name|post_date Votes table has: |votes_id|item_id|answer|total_yes|total_no What I want to do is show all items based on post_date and show the answer in the votes table with the HIGHEST total_yes. So I want to show only a SINGLE answer from the votes table with the highest total_yes vote. I was trying: SELECT a.*, b.* FROM Items a INNER JOIN Votes b ON a.item_id = b.item_id GROUP by a.item_id ORDER by a.post_date DESC, b.total_yes DESC But that doesnt work. The result I would like to see is: <item>

EDIT: I will leave the post here as is, but what I really needed to accomplish needed to be reposted. I didn't explain the problem well enough. After trying again with quite a different starting point, I was able to get the query that I needed. That is explained here . ORIGINAL QUESTION: I'm having trouble. I have looked at similar threads, and I am unable to find a solution specific to this query. The database is very large, and group by seems to slow it down immensely. The problem is I am getting duplicate results. Here is my query which causes duplicates: SELECT itpitems.identifier,

The following code works in Sage200. SELECT bcs.BomReference ,bcs.DateTimeCosted ,bcs.TotalCost FROM ( SELECT BomReference ,Max(DateTimeCosted) AS MaxDate FROM NDM_Sage200.dbo.BomCostSession BomCostSession GROUP BY BomReference ) AS ldc INNER JOIN BomCostSession AS bcs ON bcs.BomReference = ldc.BomReference AND bcs.DateTimeCosted = ldc.MaxDate ORDER BY BomReference As soon as I try extending this with an INNER JOIN to another table to get more columns (using BomReference ), I get the error message: Could not add the table ( . See below for example of modified code; I have to use 2 joins to get