Break up a SQL Server 2008 query into batches

Question

I'm trying to prepare some data for deletion by a 3rd party, and unfortunately they can only process data in batches of 2000 records. I have 100k records and may need to divide-and-export this data several more times, so I'd like to automate the process somehow.

Is there a reasonably easy way to do this using SQL Server 2008? I'm not running a complex query -- it's not too far off from SELECT PKID FROM Sometable ORDER BY PKID -- and while I can probably do this using a cursor, I'd like to know if there's a better way.

Solution 1

SET NOCOUNT ON;

CREATE TABLE [dbo].[SyncAudit] ( PkId INT, BatchNumber INT)

DECLARE  @batchsize INT
    ,@rowcount INT
    ,@batchcount INT
    ,@rootdir VARCHAR(2048)
    ,@saveas VARCHAR(2048)
    ,@query VARCHAR(2048)
    ,@bcpquery VARCHAR(2048)
    ,@bcpconn VARCHAR(64)
    ,@bcpdelim VARCHAR(2)

SET     @rootdir    = '\\SERVER1\SHARE1\FOLDER\'
SET     @batchsize  = 2000
SET     @bcpdelim   = '|'
SET     @bcpconn    = '-T' -- Trusted
--SET       @bcpconn    = '-U <username> -P <password>' -- SQL authentication

SELECT  @rowcount   = COUNT(1),
    @batchcount = CEILING(COUNT(1)/@batchsize) FROM <@TableName, string, 'SomeTable'>

SELECT [BatchSize] = @BatchSize, [BatchCount] = @Batchcount

INSERT INTO SyncAudit
SELECT 
 <@TableKey, string, 'PKField'>
 ,groupnum = NTILE(@batchcount) OVER ( ORDER BY <@TableKey, string, 'PKField'>)
FROM
<@TableName, string, 'SomeTable'>

WHILE (@batchcount > 0)
BEGIN

SET @saveas = @rootdir + 'batchnumber-' + cast(@batchcount as varchar) + '.txt'
SET @query = '  SELECT  [<@TableName, string, 'SomeTable'>].* 
                FROM    [' + db_name() + '].[dbo].[<@TableName, string, 'SomeTable'>] 
                JOIN    [' + db_name() + '].[dbo].[SyncAudit]   
                            ON  [<@TableName, string, 'SomeTable'>].<@TableKey, string, 'PKField'> = [SyncAudit].PkId 
                            AND [SyncAudit].BatchNumber = ' + cast(@batchcount as varchar) + ''

SET @bcpquery = 'bcp "' + replace(@query, char(10), '') + '" QUERYOUT "' + @saveas + '" -c -t^' + @bcpdelim + ' ' + @bcpconn + ' -S ' + @@servername
EXEC master..xp_cmdshell @bcpquery  

--EXEC (@query)


SET @batchcount = @batchcount -1
END


DROP TABLE [dbo].[SyncAudit] -- or leave for reference

Solution 2

I think you can take advantage of using ROW_NUMBER and then using BETWEEN to specify a range of rows that you like. Alternatively you could use PKID if you knew there wasn't gaps, or didn't care about the gaps

e.g.

SELECT ...
FROM
   (SELECT ... 
         ROW_NUMBER() OVER(ORDER BY PKID ) as RowNum
    FROM Sometable e
   ) t
WHERE RowNum BETWEEN @startRowIndex AND (@startRowIndex + @maximumRows) - 1

This is often used for paging results. 4GuysFromRolla have a good article on it

Solution 3

You could work out the ranges in a while @@ROWCOUNT loop to target the rows required. It may work better than ROW_NUMBER() which would have to keep numbering from the start.

declare @startid int
declare @endid int

-- get one range, these are efficient as they go over the PKID key by range
select top(1) @startid = pkid from sometable order by pkid  -- 1 key visited
select top(2000) @endid = pkid from sometable order by pkid  -- 2000 keys visited
-- note: top 2000 may end up with the 514th id if that is the last one

while @@ROWCOUNT > 0
begin
    insert otherdb.dbo.backupcopy
    select * from sometable
    where pkid between @startid and @endid

    select top(1) @startid = pkid from sometable
    WHERE pkid > @endid -- binary locate
    order by pkid

    select top(2000) @endid = pkid from sometable
    WHERE pkid > @endid -- binary locate, then forward range lookup, max 2000 keys
    order by pkid
end