SQL Server Linked Server Performance plausible solution?

Question

I am in the process to optimize a view's performance which collect data on 2 linked servers objects.

So the view is on server A. The view selects data from server B and C.

When I opened the script I noticed this view is a total mess querying multiple times the same tables over and over using sub sub sub sub selects...

To keep things simple, I will not post the actual code of the query (700+ lines) but I will create a simple query for your understanding:

      SELECT    *
      FROM      [ServerA].myDB.dbo.tableA a
                INNER JOIN [ServerA].myDB.dbo.tableB b ON a.field = b.field
                LEFT JOIN ( SELECT  SUM(field) AS mysum
                            FROM    [ServerA].myDB.dbo.tableB
                            WHERE   field IN ( SELECT   MAX(value)
                                               FROM     [ServerA].myDB.dbo.tableA
                                               WHERE    anotherField IS NOT NULL )
                          ) tbl ON tbl.mysum < b.anotherField

I know this query don't make any sense.. This is just to illustrate my point.

Would it be more performant to create a view in myDB on server A to query the tables and from Server B using a SELECT * FROM ServerA.myDB.myLocalView ?

CREATE VIEW myLocalView
AS
SELECT  *
FROM    dbo.tableA a
        INNER JOIN dbo.tableB b ON a.field = b.field
        LEFT JOIN ( SELECT  SUM(field) AS mysum
                    FROM    dbo.tableB
                    WHERE   field IN ( SELECT   MAX(value)
                                       FROM     dbo.tableA
                                       WHERE    anotherField IS NOT NULL )
                  ) tbl ON tbl.mysum < b.anotherField

Answer 1

A good solution here in my opinion would be to query the data you need and drop it into a temp table and then do the join between the temp table on the same server.

https://www.simple-talk.com/sql/t-sql-programming/temporary-tables-in-sql-server/

By pulling the data over first, and then doing the join locally, you'll see a huge improvement in performance. Trying to join from server to server is very slow due to the network lag during the join.