Redundant Join Criteria: Good or Bad Idea?
January 21, 2009 Hey, Ted
Suppose I have four tables that I commonly join. Is there any benefit to adding redundant criteria to the join? Or to the “where” clause? That is, will redundant criteria or selection expressions improve performance? –Philip Philip’s four tables are keyed as follows: SITE ITEM PROCESS STRUCTURE ------ ------ -------- --------- SiteID SiteID SiteID SiteID ItemID ItemID ItemID Revision Revision Revision StructID Here’s a join without redundant join criteria: select whatever from site as s join item as i on s.siteid = i.siteid join process as p on i.siteid = p.siteid and i.itemid = p.itemid and i.rev = p.rev join |