Mysql in statement performance related with its position?

浏览数：17 / 时间：2015年06月12日 
select
    *
from
    (
    select
        event_date,
        ‘2014-12-06‘ as active_date,
        channel_id,
        new_user_count as new_user_count,
        1d_retain/new_user_count as 1d_retain_rate
    from
        web_channel_retain
    where
        app_id=-1
    and
        event_date=‘2014-12-05‘
    and
        new_user_count>= 500
    and
        channel_id in (select distinct channel_id from formated_channel_category where type_id=507 )
    )as f
order by 1d_retain_rate desc
limit 0,50;

The above sql runs less than 2 seconds, while below sql runs a long time(I killed it before it completed). The only difference is the position of in statement.

select
    *
from
    (
    select
        event_date,
        ‘2014-12-06‘ as active_date,
        channel_id,
        new_user_count as new_user_count,
        1d_retain/new_user_count as 1d_retain_rate
    from
        web_channel_retain
    where
        channel_id in (select distinct channel_id from formated_channel_category where type_id=507 )
    and
        app_id=-1
    and
        event_date=‘2014-12-05‘
    and
        new_user_count>= 500
        
    )as f
order by 1d_retain_rate desc
limit 0,50;

 

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