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c#sqlsql-serverlinq
Feldel
Feldel

Reputation: 11

C# update database table using SQL using values from a DataTable that is not in SQL Server

I have a SQL Server database table that I need to update with values that I have in a C# application DataTable retrieved from an outside source (it could be from file, external API call, etc I guess it is irrelevant).

Is there a way to do a "mass" update using SQL similar to:

UPDATE myTable1 t1
SET    custAddress = t2.address
FROM   myTable2 t2
WHERE  t1.id = t2.id

I suppose I could use the above example as long as both tables are in the same SQL Server database; but in this case, myTable2 is an application (C#) DataTable and not a SQL Server table.

Is there a way to accomplish the update similar to the one above?

I know I could "loop" through each of the application table rows and trigger a SQL update for each row, but if my data table has thousands of rows, I would not want (whenever possible) to have to execute one SQL update for each row that I need to update.

Any help would be appreciated. I am open to solutions or suggestion that involve LINQ or any other C# or SQL logic.

Upvotes: 1

Views: 1108

Answers (2)

William Xifaras
William Xifaras

Reputation: 5312

I think the most straightforward way to accomplish this is to do a bulk insert of your application data using SqlBulkCopy into a staging table. There is also an option to set the batch size if you want to do this in batches.

After the bulk insert, run a stored procedure to do the update. Another option is to use an after insert trigger, but that seems to only make sense if you bulk insert in batches.

Upvotes: 1

granadaCoder
granadaCoder

Reputation: 27904

  1. Take the data-table (C#) and convert it to xml. Hint, if you add the data-table to a data-set, you can call ds.GetXml(). (See here)

  2. Push the xml to sql-server.

  3. "Shred" the xml into #temp or @variable table(s) using sql-server-xml functionality.

  4. Perform CUD (create/update/delete) operations using the data in the #temp or @variable tables.

The basic idea is here:

HOW TO: Perform Bulk Updates and Inserts Using OpenXML with .NET Providers in Visual C# .NET

But you don't want to use OPENXML (Sql Server 2000 syntax), instead, use examples for "shredding found here:

http://pratchev.blogspot.com/2007/06/shredding-xml-in-sql-server-2005.html

IMHO : This is a great way to do "set based" operation for CUD (create/update/delete). One of the biggest bonuses of doing it this way is that all the index-updating happens after the set based operation, where if you do it RBAR (row by agonizing row), the index(es) has to rebuild after each single operation. :(

Note, #3 (b) is optional. You have to shred. BUT, you could go straight from xml-shredding to the "real" tables (and skip the #temp or @variable table). I usually test a real world "load" (amount of xml data) and if it doesn't make much difference, I stick with #temp or @variable tables. Its easier to debug later, because you can put in a temp "select * from #myTempTable" and see if the data got shredded correctly. You should also test #temp vs @variable tables as well. Sometimes it makes a difference.

Please note there is an old-old "performance" bug on element-based-xml.

https://connect.microsoft.com/SQLServer/feedback/details/250407/insert-from-nodes-with-element-based-xml-has-poor-performance-on-sp2-with-x64

It may no longer apply. But it is something to be aware of. "back in the day" (because of the injected bug) my team and I had to change our element-based-xml into attribute-based xml (in C#) before sending it down to sql-server.

Upvotes: 2

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