On 14/10/10 17:28, Dan Kennedy wrote: > > On Oct 14, 2010, at 10:43 PM, Alan Chandler wrote: >> CREATE TABLE div_winner_pick ( ... >> PRIMARY KEY (cid,confid,divid,uid) >> );
... >> >> CREATE INDEX div_win_pick_uid_cid_idx ON div_winner_pick (uid,cid); ... > It should be clearer. Basically the index would be redundant > if it contains the same columns in the same order as the primary > key. Or a prefix thereof. i.e. the following indexes would be > all be redundant (pure overhead for no benefit): > > CREATE INDEX x ON div_pick_winner(cid); > CREATE INDEX x ON div_pick_winner(cid,confid); > CREATE INDEX x ON div_pick_winner(cid,confid,divid); > CREATE INDEX x ON div_pick_winner(cid,confid,divid,uid); > > Your index is not redundant though. This is interesting - what if I changed the primary key to be PRIMARY KEY (uid,cid,confid,divid) Is that an optimisation that is useful to make? -- Alan Chandler http://www.chandlerfamily.org.uk _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
