Mysql Query(where and group)
===

I have 2 tables

**tbl_activities**

     id | activity 
     1  | activity1
     2  | activity2
     
**tbl_sub_activities** 
 
    id |activityId   | subActivity   | status 
     1 |  1          | subActivity1  | done
     2 |  1          | subActivity2  | done
     3 |  1          | subActivity3  | ongoing
     4 |  2          | subActivity4  | done
     5 |  2          | subActivity5  | done


Scenario:
An activity can have many subactivities.

if status of subactivity are all done, then activity is done,
if status of subactivity still has an ongoing, the activity is ongoing.

Question :
How can I query tbl_activities to have an output like this.

     id | activity  | status
     1  | activity1 | ongoing
     2  | activity2 | done

I've done this using php but I wanna know how to do this using SQL query.
 