Pavlo wrote: > What I have is one big table storing all mandatory properties of an entity > and several small tables, storing optional properties. > > So, when I need to select big number of elements using JOIN the probability > of optional properties is low. > And so, for every row from big table there will be ~99% of join lookups in > small tables leading to NULLs. > > So I got an idea to store flags in big table telling me whether optional > property is present (flag). > I want to lookup small tables only when flag is set but I can't see how to > tell SQLite to skip JOIN lookup for certain rows and return NULLs.
SELECT * FROM Big LEFT JOIN Small ON Big.flag AND Big.ID = Small.BigID However, for small tables, the IDs will be in the cache anyway. It is unlikely that this will make any noticeable difference. Regards, Clemens _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
