in this code-
CREATE TABLE `tablename` (
`id` int(10) unsigned NOT NULL auto_increment,
`a` varchar(10) NOT NULL,
`b` varchar(45) default NULL,
`c` varchar(45) NOT NULL,
`d` varchar(45) default NULL,
PRIMARY KEY (`id`),
KEY `Index_a` (`a`),
KEY `Index_bcd` (`b`,`c`,`d`),
KEY `Index_cd` (`c`,`d`)
) ....;
what do the lines that start with KEY?
I know PRIMARY KEY sets the pk of the table.. but I don't understand the rest of the lines..
does that have to do something with setting indexes to make searches faster? or something like that?