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From: Erland Sommarskog <esquel@sommarskog.se>
Newsgroups: comp.databases.ms-sqlserver
Subject: Re: SELECT DISTINCT and compound primary key.
Date: Tue, 07 Jun 2011 23:37:33 +0200
Organization: Erland Sommarskog
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Richard (richardemig@gmail.com) writes:
> I have a table (Main) with compound key and second, temporary table
> (Temp) with same fields but without PK. Main table key is 3 columns
> ( SourceFileHash, FileHash, PathHash ). There is also 4 other columns
> in each table.
> My intent is to use temp table to store batches of records with
> duplicates and inserting only unique records to main table after every
> batch is finished ( batches are inserted using SqlBulkCopy ).
> 
> How can I select distinct records on Temp table but using only 3 PK
> columns ?
> 
> Here is query that I created - it won't work because it is trying to
> insert duplicate records to main:
 
WITH numbered AS (
    SELECT sourceFileHash, pathHash, fileHash, length, creationDate,
           modificationDate, lastAccessDate, line,
           row_number() OVER 
             (PARTITION BY sourceFileHash, pathHash, fileHash
              ORDER BY  ?????) as rowno
    FROM   CatalogEntriesTemp
)
SELECT sourceFileHash, pathHash, fileHash, length, creationDate,
       modificationDate, lastAccessDate, line
FROM   numbered
WHERE  rowno = 1

You need to fill in the ORDER BY clause to determine which of the
rows with the same duplicate key you want.

 


-- 
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se

Links for SQL Server Books Online:
SQL 2008: http://msdn.microsoft.com/en-us/sqlserver/cc514207.aspx
SQL 2005: http://msdn.microsoft.com/en-us/sqlserver/bb895970.aspx