Acting on sql result row count - sql

Question

I'm starting with this query:
SELECT TOP 1 Parties.FirstName + ' ' + Parties.MiddleName + ' ' + Parties.LastName AS Plaintiffs
FROM Jackets INNER JOIN
JacketPartyLinks ON Jackets.Id = JacketPartyLinks.Jacket_JacketPartyLink INNER JOIN
Parties ON Parties.Id = JacketPartyLinks.JacketPartyLink_Party
WHERE (Jackets.Id = #JacketID) AND (JacketPartyLinks.Role = 0)
What I'd like to accomplish is to take a count of what's returned, and if it's one row, do nothing. If it's more than one row, add something like ", et al". Notice that this query returns a single column, and it while it should be able to run standalone, it also needs to work as a subquery.
How can this be done?
EDIT: Add TOP 1

Answer 1

Use top and count..over and then wrap it in an outer query, like so:
select
Plantiffs + case when PlantiffCount > 1 then ', et al' else '' end as Plantiffs
from
(
SELECT TOP 1
Parties.FirstName + ' ' + Parties.MiddleName + ' ' + Parties.LastName as Plantiffs,
count(1) over () as PlantiffCount
FROM
Jackets
INNER JOIN JacketPartyLinks ON
Jackets.Id = JacketPartyLinks.Jacket_JacketPartyLink
INNER JOIN Parties ON
Parties.Id = JacketPartyLinks.JacketPartyLink_Party
WHERE
(Jackets.Id = #JacketID) AND (JacketPartyLinks.Role = 0)
order by Parties.LastName asc
) x
The over () part after count tells it to count all rows and not group by anything. This is why there isn't a group by clause in that query. You can use over with any aggregate function, which is pretty nifty.