Sql-server – Informix top command

I have had the best success when doing similar tasks with the following flow:

1. Copy the data to keep into a temporary table
2. Truncate the original table to purge all data
3. Move everything from the temporary table back into the original table

One major benefit of this is that your indexes will be rebuilt as you put the data back into the original table.

According to this article, the temp DB is used if sorting required more memory than SQL Server has allocated.

If you sort over a column that is not indexed, the database server will perform a full table scan and keep track of all Date_Ordered values (and primary key values) of all records in the table.

Create an INDEX on Orders.Date_Ordered to speed up sorting and reduce memory usage.