two tables are as follows .
CREATE TABLE table_a
( id
int(11) NOT NULL, col1
date NOT NULL, PRIMARY KEY (id
), KEY col1
(col1
))
CREATE TABLE table_b
( id
int(11) NOT NULL, col1
varchar(255) NOT NULL, PRIMARY KEY (id
))
and then a query is
select a.id, b.col1, a.col1 from table_a a, table_b b where a.id=b.id order by a.col1 desc;
this query always does filesort. why?
col1 column on table_a is arleady indexed.
does simple ‘order by’ query on joined tables always filesort?
how can i prevent mysql from filesorting.
help me please…