On 27 June 2011 16:16, hilaner <hila...@poczta.onet.pl> wrote: > I have hundred thousands of records in this table: > > CREATE TABLE days ( > day_id INTEGER NOT NULL PRIMARY KEY, > day_date DATE > ); > > CREATE INDEX day_i ON days (day_date ASC); > > And then if I run such query: > > EXPLAIN QUERY PLAN > SELECT JULIANDAY(MAX(day_date)) FROM days; > 0|0|0|SCAN TABLE days (~1000000 rows) > > it will do full table scan instead of use an index. > > But: > > EXPLAIN QUERY PLAN > SELECT MAX(day_date) FROM days; > 0|0|0|SEARCH TABLE days USING COVERING INDEX day_i (~1 rows) > > so it is as I expected. > > Is there any other way to rewrite such kind of queries with functions? > The query below uses an index but it is much longer: > > EXPLAIN QUERY PLAN > SELECT JULIANDAY(day_date) FROM days > WHERE day_date IN (SELECT MAX(day_date) FROM days); > 0|0|0|SEARCH TABLE days USING COVERING INDEX day_i (day_date=?) (~250 rows) > 0|0|0|EXECUTE LIST SUBQUERY 1 > 1|0|0|SEARCH TABLE days USING COVERING INDEX day_i (~1 rows)
select julianday( ( select max( day_date ) from days ) ); > > Best regards, > Adam Regards, Simon _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
