mysql - How to optimize SQL query? Keys are not being used -


how can optimize following query? have tried create indexes (idx_events, idx_events_startdate, don't help. query takes 10s far much.

.... 131 rows in set (10.25 sec)  mysql> explain select results.event results                 inner join events on results.event=events.id                  (datediff(now(), events.startdate) < 30)                 , (datediff(now(), events.startdate) > -1)                 , results.status='ok'                 group events.id; +----+-------------+---------+--------+----------------------------------------------+------------+---------+-----------------------+--------+---------------------------------------------------------------------+ | id | select_type | table   | type   | possible_keys                                | key        | key_len | ref                   | rows   |                                                               | +----+-------------+---------+--------+----------------------------------------------+------------+---------+-----------------------+--------+---------------------------------------------------------------------+ |  1 | simple      | results | ref    | idx_event,idx_status                         | idx_status | 53      | const                 | 773425 | using index condition; using where; using temporary; using filesort | |  1 | simple      | events  | eq_ref | primary,idx_events_name,idx_events_startdate | primary    | 4       | eventor.results.event |      1 | using                                                         | +----+-------------+---------+--------+----------------------------------------------+------------+---------+-----------------------+--------+---------------------------------------------------------------------+ 2 rows in set (0.01 sec)

wrapping indexed column in function prevents optimiser using it. looks need free index on startdate nice filtered result set join:

select r.event results    join events e     on e.id = r.event    , e.startdate > curdate() - interval 30 day    , e.startdate < curdate() + interval 1 day  r.status = 'ok'

i placing joined table conditions in on clause , using table aliases possible.

i'd prefer integer status column string 'ok', can foreign key status table description if need it.

as added aside.. use >= , < date ranges, if example, startdate datetime or timestamp, query exclude values 2014-08-01 00:00:00 if on cut off of curdate() - interval 30 day.


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