mysql - Find number of "active" rows each month for multiple months in one query -

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i have mysql database each row containing activate , deactivate date. refers period of time when object row represents active.

activate     deactivate   id 2015-03-01   2015-05-10   1 2013-02-04   2014-08-23   2

i want find number of rows active @ time during each month. ex.

jan: 4 feb: 2 mar: 1 etc...

i figured out how single month, i'm struggling how 12 months in year in single query. reason in single query performance, information used , caching wouldn't make sense in scenario. here's code have month @ time. checks if activate date comes before end of month in question , deactivate date not before beginning of period in question.

select * tblname activate <= date_sub(now(), interval 1 month) , deactivate >= date_sub(now(), interval 2 month)

if has idea how change , grouping such can indefinite number of months i'd appreciate it. i'm @ loss how group.

if have table of months care about, can do:

select m.*,        (select count(*)         table t         t.activate_date <= m.month_end ,               t.deactivate_date >= m.month_start        ) actives months m;

if don't have such table handy, can create 1 on fly:

select m.*,        (select count(*)         table t         t.activate_date <= m.month_end ,               t.deactivate_date >= m.month_start        ) actives (select date('2015-01-01') month_start, date('2015-01-31') month_end union       select date('2015-02-01') month_start, date('2015-02-28') month_end union       select date('2015-03-01') month_start, date('2015-03-31') month_end union       select date('2015-04-01') month_start, date('2015-04-30') month_end      ) m;

edit:

a potentially faster way calculate cumulative sum of activations , deactivations , take maximum per month:

select year(date), month(date), max(cumes) (select d, (@s := @s + inc) cumes       (select activate_date d, 1 inc table t union             select deactivate_date, -1 inc table t            ) t cross join            (select @s := 0) param       order d      ) s group year(date), month(date);

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