Update large number of rows - SQL Server 2005
I have several tab-separated files which I would like to use to update a large number of rows. So far I have naively created a temp table and imported the data into it and then updated the table which also involved a join. This created a large trans log. I would like to prevent this and do it in chunks. I have found this:
http://itknowledgeexchange.techtarget.com/itanswers/bulk-update-in-sql-server-2005/
Is this the best way?
Are there even faster methods (SSIS, bcp)?
Any feedback highly appreciated. Thanks.
Christian
PS:
My naive code looks like this. Unfort. i is not a primary key (the table has one as Bla is a child of another table)
drop table #temp
crea开发者_StackOverflow中文版te table #temp
(
i int,
xml nvarchar(max)
)
BULK INSERT #temp
...
update a
set XML = b.xml
from Bla as a
inner join #temp as b on a.i = b.i
Do you have an indexed identity column in the target table? This is one of the few cases where I actually like to use a WHILE loop. The main problem with the solution in the link you posted is bad index usage.
DECLARE @START INT, @FINISH INT, @LOOPEND INT
SELECT @START = 1, @FINISH = 5000, @LOOPEND = MAX(ID)
from Bla
WHILE @START <= @LOOPEND
BEGIN
update a
set XML = b.xml
from Bla as a
inner join #temp as b on a.i = b.i
WHERE a.ID BETWEEN @START AND @FINISH
SET @START = @FINISH + 1
SET @FINISH = @FINISH + 5000
END
In cases where you have a surrogate key (identity column as primary key), which is not so uncommon, this would cause a simple index seek on the primary key and is adjustable simply by the growth amount (5000 in the example)
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