database - MySQL query takes ages to return on a huge table -

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i have big table , following code takes 990 sec. complete. bdate , itype indexed. else need optimize/change?

select s, count(*) total  `mt_ex_15`  bdate > '2014-10-01' , bdate < '2014-11-01' , itype = '3' group s order total desc

edit: here explain

id  select_type table   type    possible_keys   key key_len ref rows       1   simple  mt_ex_15    ref itype,bdate,s   itype   2   const   44157686    using where; using temporary; using filesort

edit: think need optimize db or my.cnf because following query took 40 secs.

select count(*) total  `mt_ex_15`  bdate > '2015-02-01' , bdate < '2015-03-01'

and here explain:

 id     select_type     table   type    possible_keys   key     key_len     ref     rows       1   simple  mt_ex_15    range   bdate   bdate   3   null    4494019     using where; using index

for query:

select s, count(*) total  `mt_ex_15`  bdate > '2014-10-01' , bdate < '2014-11-01' , itype = '3' group s order total desc

the best index mt_ex_15(itype, bdate, s). engine should able take full advantage of index where clause. in addition, covering index original data not need touched query.

if had list of available "s" values, correlated subquery:

select s.*,        (select count(*)         mt_ex_15 m         m.s = s.s , m.itype = 3 , m.bdate > '2014-10-01' , m.bdate < '2014-11-01'        ) total s having total > 0 -- using convenient mysql extension order total desc;

the best index query mt_ex_15(s, itype, bdate).

note: if itype integer, should remove quotes around constant. misleading.


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