Den 2012-07-23 00:24 skrev Leyne, Sean såhär: > > Kjell, > > > Trying to figure out a way to do a search/query with decent performance. > > > > Table "Master" contains roughly 100 million records and table "Detail" > > contains roughly 200 million records. > > > Unfortunately, this will cause a natural scan of the 100 million record > > "Master" table, and roughly 200 million subselects... > > > > Can anyone figure out a way to avoid a full table scan? > > What is the "selectivity" of Detail rows to Master (What % of Master > don't have Details)? >
I'd say something like one master of about 100-1000 would have no details, i.e. probably at least 99 percent do have at least one detail. > I am afraid that there won't be much that can be done to avoid the > basic problem. > :-( Kjell -- -------------------------------------- Kjell Rilbe DataDIA AB E-post: [email protected] Telefon: 08-761 06 55 Mobil: 0733-44 24 64 [Non-text portions of this message have been removed] ------------------------------------ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Visit http://www.firebirdsql.org and click the Resources item on the main (top) menu. Try Knowledgebase and FAQ links ! Also search the knowledgebases at http://www.ibphoenix.com ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/firebird-support/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/firebird-support/join (Yahoo! ID required) <*> To change settings via email: [email protected] [email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
