The order of fields in the multicolumn index matters. Taken in the order of fields in the index, the first inequality relation terminates the part of the index that is usable.
For a constraint "plate EQUALS and date BETWEEN" you need an index on (plate,date). Your index is only usable for "date EQUALS and plate BETWEEN" -----Urspr?ngliche Nachricht----- Von: sqlite-users-bounces at mailinglists.sqlite.org [mailto:sqlite-users-bounces at mailinglists.sqlite.org] Im Auftrag von Michele Pradella Gesendet: Freitag, 19. Februar 2016 09:07 An: sqlite-users at mailinglists.sqlite.org Betreff: [sqlite] Multiple Column index Hi all, I have a question about using index with multiple column. Take this test case CREATE TABLE test (DateTime BIGINT,CarPlate VARCHAR(255)); CREATE INDEX indexA ON test(DateTime); CREATE INDEX indexB ON test(CarPlate); CREATE INDEX indexAB ON test(DateTime,CarPlate); now if you do [1] -> EXLPAIN QUERY PLAN SELECT * FROM test WHERE (DateTime=0) AND (CarPlate='AA000BB') you obtain: 0|0|0|SEARCH TABLE test USING COVERING INDEX indexAB (DateTime=? AND CarPlate=?) So it's good. if you do EXLPAIN QUERY PLAN SELECT * FROM test WHERE (DateTime>1)AND(DateTime<100) AND (CarPlate = 'AA000BB'); 0|0|0|SEARCH TABLE test USING INDEX indexB (CarPlate=?) So is used only the indexB not the index for DateTime, and if you force it indexAB 0|0|0|SEARCH TABLE test USING COVERING INDEX indexAB (DateTime>? AND DateTime<?) so it used only for DateTime. Do you think Is there a way to use indexAB (or using both index combining two select) to cover both condition (DateTime>X AND DateTime<Y and CarPlate = 'something' )? multicolumn index can be used only for [1] queries? _______________________________________________ sqlite-users mailing list sqlite-users at mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users ___________________________________________ Gunter Hick Software Engineer Scientific Games International GmbH FN 157284 a, HG Wien Klitschgasse 2-4, A-1130 Vienna, Austria Tel: +43 1 80100 0 E-Mail: hick at scigames.at This communication (including any attachments) is intended for the use of the intended recipient(s) only and may contain information that is confidential, privileged or legally protected. Any unauthorized use or dissemination of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by return e-mail message and delete all copies of the original communication. Thank you for your cooperation.
