Query performance is improved because additional sort operations are not necessary and unnecessary data copies are not required.The following example uses the MERGE statement to bulk load data from column in the data source, which maps to the clustered index key column in the target table.When checked the session it was actively reading data and longops suggested that it would take more than a day to complete.Wondering why I realised that postcode was not indexed on table 2.Before running this example, create a text file named 'Stock Data.txt' in the folder C:\SQLFiles\. Stock AS s USING OPENROWSET ( BULK 'C:\SQLFiles\Stock Data.txt', FORMATFILE = 'C:\SQLFiles\Bulkload Format File.xml', ROWS_PER_BATCH = 15000, ORDER (Stock) UNIQUE) AS b ON s. The file should have two columns of data separated by a comma.
When using the TOP clause in the MERGE statement for this purpose, it is important to understand the following implications.
By doing so, the entire file is processed in a single batch.
To improve the performance of the bulk merge process, we recommend the following guidelines: These guidelines ensure that the join keys are unique and the sort order of the data in the source file matches the target table.
Typically, this is done by executing a stored procedure or batch that contains individual INSERT, UPDATE, and DELETE statements.
However, this means that the data in both the source and target tables are evaluated and processed multiple times; at least once for each statement.