mysql - Select latest updated categories based on their items -

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i have mysql database , there's categories table this:

id  name            parent -------------------------- 1   news            0 2   analysis        0 3   europe          1 4   middle east     1 5   asia            1 6   americas        1 7   commentaries    2 8   interviews      2 9   articles        2 10  reports         2

and items table this:

id  created                 catid   title --------------------------------------------- 1   2013-08-12 20:15:00     3       foo 2   2013-08-12 19:15:00     3       bar 3   2013-08-12 18:15:00     4       foobar 4   2013-08-12 17:15:00     4       barfoor 5   2013-08-12 16:15:00     8       boofar 6   2013-08-12 15:15:00     9       farfar 7   2013-08-11 16:45:00     10      farfarbar 8   2013-08-11 16:15:00     5       foofoobar 10  2013-08-10 16:15:00     7       foobarbar

what want list categories children of specified parent , have latest items in them. example if want latest updated categories of news (catid=1) section, result be:

3   europe 4   middle east 5   asia

note results ordered last update time.

please consider due large amount of records, performance of query important.

a join works pretty fast. use group enable aggregate max()-function sort output.

in where-clause can choose parent-id want search for.

select c.id, c.name categories c inner join items on c.id = i.catid c.parent = 1 group c.id order max(i.created) desc

sql-fiddle

edit

in event of single nestings, can change query follows:

select c.id, c.name categories c inner join items on c.id = i.catid c.parent = 1 or c.parent in (select id categories c.parent = 1) group c.id order max(i.created) desc

sql-fiddle

if need more nestings, you'd need create stored procedures. more information can found here.


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