Error while posting to a table - sql

Question

Platform used:
SQL Server 2008 and C++ Builder
I am doing an inner join between 2 tables which was giving me an error:
Row cannot be located for updating
Query:
SELECT DISTINCT
b.Acc, b.Region, b.Off, b.Sale, a.OrgDate
FROM
sales b
INNER JOIN
dates a ON (a.Acc = b.Acc and a.Region = b.Region and a.year= b.year)
WHERE
(a.xdate <> a.yDate)
and (b.Sale = a.SaleDate)
and b.year = 2010
Note: Acc, Region, Off are primary keys of table b and are also present in table a.
Table a has an id which is the primary key which does not appear in the query.
It turned out that my inner join was returning duplicate rows.
I changed my inner join query to use 'DISTINCT' so that only distinct rows are returned and not duplicate. The query runs but then I get the error:
Insufficient key column information for updating or refreshing.
It does turn out that the fields which are primary keys in Table A have the same names as the fields in Table B
I found that this is a bug which occurs while updating ADO record-sets.
BUG: Problem Updating ADO Hierarchical Recordset When Join Tables Share Same Column Name
I have the following 2 questions:
Is it not a good idea to use Distinct on an inner join query?
Has anyone found a resolution for that bug associated with TADO Query's?
Thank you,

Answer 1

The way I would solve this is to construct an update query by hand and run it through TADOQuery.ExecSQL. That assumes you actually know what you are doing.
The question is WHY are you working on a recordset that results in multiples of the same row, on all fields? You should be inspecting your query and fixing it. DISTINCT doesn't help, because SQL Server has picked one record but ADO won't know which one it picked, since there isn't enough information to properly identify the source on each side of the JOIN.
This query pulls in a.id to make the source records identifiable:
SELECT Acc,Region,Off,Sale,OrgDate,id
FROM
(
SELECT b.Acc,b.Region,b.Off,b.Sale,a.OrgDate, a.id,
rn=row_number() over (partition by b.Acc,b.Region,b.Off order by a.id asc)
FROM sales b
JOIN dates a ON(a.Acc = b.Acc and a.Region = b.Region and a.year= b.year)
WHERE a.xdate <> a.yDate
and b.Sale = a.SaleDate
and b.year = 2010
) X
WHERE rn=1;
Not tested, but it should work with ADO