如果我在第4栏上有索引: from varchar(20) NOT NULL, departuredate NOT NULL, ....KEY mykey(from, to, departure, arrival)当我只对from和to进行均匀度查询时,是否需要创建一个额外的索引KEY fromto (from
varchar(200),) ENGINE=InnoDB;MySQL------+----------+--------+------+------------+---------+---------------+---------+------------+MySQL----------------++--------------------+
1 row in