mysql select query is very slow and uses filesort - mysql

Question

I have one big problem in the slow query select
0.3054 sec
this the query
SELECT id, ar_name, en_name,product_id,havproduct, viewnum, uid,pin_to, sid, ssid,cid, close,date
FROM subject
where active = '1' and deleted = '0' and cid= '24'
order by id DESC
LIMIT 0,30
and when i use this
explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE subject ALL NULL NULL NULL NULL 230026 Using where; Using filesort
and this table create
CREATE TABLE `subject` (
`id` int(11) NOT NULL,
`cid` int(11) NOT NULL,
`did` int(11) NOT NULL,
`sid` int(11) NOT NULL,
`ssid` int(11) NOT NULL,
`product_id` int(11) NOT NULL DEFAULT '0',
`havproduct` int(11) NOT NULL DEFAULT '0',
`uid` int(11) NOT NULL,
`ar_name` varchar(500) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
`en_name` varchar(500) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL,
`close` int(11) NOT NULL DEFAULT '0',
`active` int(11) NOT NULL,
`date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`viewnum` int(11) NOT NULL DEFAULT '1',
`pin_to` int(11) NOT NULL DEFAULT '0',
`deleted` int(11) NOT NULL,
`user_active` int(11) NOT NULL DEFAULT '1',
`dep_active` int(11) NOT NULL DEFAULT '1'
) ENGINE=MyISAM DEFAULT CHARSET=utf8
and the table have 200000 record or more from data

Answer 1

You have no keys on your data. For your particularly query, the best index is:
create index id_subject_4 on subject(active, deleted, cid, id)
By the way, you should only use single quotes for string and date constants. All the values in your query are integers, so remove the quotes:
SELECT id, ar_name, en_name,product_id,havproduct, viewnum, uid, pin_to, sid, ssid,cid, close,date
FROM subject
where active = 1 and deleted = 0 and cid = 24
order by id DESC
LIMIT 0, 30;