Big/Big Table Joins

In a project, I see a large table with 13 millions records join with another tables with 13 million records, but due to business requirement, the select statement does not include where clause.

In the situation, I think that index is not helpful. My colleague thought that index is useful, and without testing, he created it. I checked this and found that time to create index + time to query using the index > time to query without index.

http://blog.kejser.org/2012/07/19/bigbig-table-joins/