How to add a break-out aggregate row group in SSRS - sql-server

Question

I know virtually nothing about SSRS, so forgive me if I'm using the wrong vocab.
The group I'm working for has a list of volunteer opportunities. Each opportunity has a specified number of volunteers needed. The database keeps track of people who have volunteered, for which opportunity they volunteered, and the status of their volunteering: whether they've just signed up and need to be contacted, whether they're somewhere in the process of becoming a volunteer, whether they are volunteering, or whether they've quit volunteering.
Certain volunteer opportunities (i.e. those requiring contact with children and therefore requiring a background check), have more volunteer states than the rest of the opportunities. For these opportunities there are a total of 14 states, compared to 3 or 4 for the rest.
I need to create a report that displays the counts of people in each state for each opportunity. It's unreasonable for there to be 15 columns (14 + the volunteers needed) for states when most have only three. For children-related opportunities, I want to specify an 'other' column, and have a expansion [+] to the left of the volunteer opportunity name which will expand out all the children-specific states with their associated counts.
The report as it is now looks like this:
My background is in database/query design, so naturally I wrote a query with a joined sub-query for each of the columns. Rather than making an additional new subquery for each of the 'Other' states, I assume there's a way that I can have a single subquery join grouping on the volunteer status, and let SSRS do the rest of the work. (I may be wrong about SSRS's capabilities here.)
My proposed query looks something like this:
SELECT vo.name, vo.volunteers_needed, vm.status, vm.status_count
FROM tbl_volunteer_opportunity vo
JOIN (SELECT volunteer_opp_id, status, COUNT(*) "status_count"
FROM tbl_volunteer_opportunity_member
GROUP BY volunteer_opp_id, status) vm ON vo.volunteer_opp_id = vm.volunteer_op_id
I now need to make a tablix and/or datasource to make columns for the Connected, In Process, No Contact, and an aggregate for Other values, and then do something else for a expansion for each of the Other statuses.
I'm not sure how to do either of those things.

Answer 1

Assuming you have a query that returns data in the following format:
+-------------+--------------------+-------------+-------+
| ProfileName | Status | StatusGroup | Count |
+-------------+--------------------+-------------+-------+
| A | Needed | Needed | 5 |
| A | Connected | Connected | 3 |
| A | In Process | In Process | 5 |
| A | No Contact | No Contact | 2 |
| A | Other status | Other | 3 |
| A | Another status | Other | 6 |
| A | Yet another status | Other | 2 |
+-------------+--------------------+-------------+-------+
You then create a tablix that uses the ProfileName as a row grouping, and the StatusGroup as a column group. The tablix will look like this in the designer:
+-----------------+
| [StatusGroup] |
+-----------------+-----------------+
| [ProfileName] | [Sum(Count)] |
+-----------------+-----------------+
You can then add a totel column on the right, and add an additional level to the column group with interactive expand/collapse functionality (to expand the "Other" StatusGroup into the individual statuses). Using SSRS expressions, you should be able to hide the expand/collapse button on the column headers of the StatusGroups that are not "Other".
Hope this is enough to get you started.