我可以在没有往返的情况下将Select语句的结果插入另一个表吗？

Question

I have a web application that is written in MVC.Net using C# and LINQ-to-SQL (SQL Server 2008 R2).

I'd like to query the database for some values, and also insert those values into another table for later use. Obviously, I could do a normal select, then take those results and do a normal insert, but that will result in my application sending the values back to the SQL server, which is a waste as the server is where the values came from.

Is there any way I can get the select results in my application and insert them into another table without the information making a roundtrip from the the SQL server to my application and back again?

It would be cool if this was in one query, but that's less important than avoiding the roundtrip.

Assume whatever basic schema you like, I'll be extrapolating your simple example to a much more complex query.

Answer 1

Can I Insert the Results of a Select Statement Into Another Table Without a Roundtrip?

From a "single-query" and/or "avoid the round-trip" perspective: Yes.

From a "doing that purely in Linq to SQL" perspective: Well...mostly ;-).

The three pieces required are:

• The INSERT...SELECT construct:
  By using this we get half of the goal in that we have selected data and inserted it. And this is the only way to keep the data entirely at the database server and avoid the round-trip. Unfortunately, this construct is not supported by Linq-to-SQL (or Entity Framework): Insert/Select with Linq-To-SQL

• The T-SQL OUTPUT clause:
  This allows for doing what is essentially the tee command in Unix shell scripting: save and display the incoming rows at the same time . The OUTPUT clause just takes the set of inserted rows and sends it back to the caller, providing the other half of the goal. Unfortunately, this is also not supported by Linq-to-SQL (or Entity Framework). Now, this type of operation can also be achieved across multiple queries when not using OUTPUT , but there is really nothing gained since you then either need to a) create a temp table to dump the initial results into that will be used to insert into the table and then selected back to the caller, or b) have some way of knowing which rows that were just inserted into the table are new so that they can be properly selected back to the caller.

• The DataContext.ExecuteQuery<TResult> (String, Object[]) method:
  This is needed due to the two required T-SQL pieces not being supported directly in Linq-to-SQL. And even if the clunky approach to avoiding the OUTPUT clause is done (assuming it could be done in pure Linq/Lambda expressions), there is still no way around the INSERT...SELECT construct that would not be a round-trip.

Hence, multiple queries that are all pure Linq/Lambda expressions equates to a round-trip.

The only way to truly avoid the round-trip should be something like:

var _MyStuff = db.ExecuteQuery<Stuffs>(@"
    INSERT INTO dbo.Table1 (Col1, Col2, Col2)
    OUTPUT INSERTED.*
       SELECT Col1, Col2, Col3
       FROM   dbo.Table2 t2
       WHERE  t2.Col4 = {0};",
       _SomeID);

And just in case it helps anyone (since I already spent the time looking it up :), the equivalent command for Entity Framework is: Database.SqlQuery<TElement> (String, Object[])

Answer 2

根据您的要求尝试此查询

insert into IndentProcessDetails (DemandId,DemandMasterId,DemandQty) ( select DemandId,DemandMasterId,DemandQty from DemandDetails)