How to properly specify condition: sum count = column value? - sql-server

Question

Im updating a system, trying to create a 'shadow' table of an orignal table, reciving changes through triggers, but not using the orginal table, since I really don't like the way the orignal program is designed.
One of them is a team configuration table, holding all the users & their team id. Users with the same team id are of the same team. I am trying to create trigger here to intercept data into a new team history log. (1 row / 1 team id)
But since after a team setup, multiple rows of the table get updated, and update is not done in batch, it's hard to tell when a new team setup is over. Fortunately there is this member_count column, which can be used to count the members and determine when all the nencessry records related to this new team_id are updated.
| team id | uid | member_count |
|201701010800A| 1 | 3 |
|201701010800A| 2 | 3 |
|201701010800A| 3 | 3 |
My question is how should I specify this condtition in after-update trigger.
here is what I do for now. But it seems so hacky. I guess there are more sensible ways to express it.
if exists(
select 1 from ( values (1) ) t(c)
outer apply (
select count(team_id) tc, max(member_count) mx, min(member_count) mm
from old_teamtable
where team_id = ( select top 1 team_id from inserted )
) e
where tc = mx and mx = mm
)

Answer 1

Does this work for you?
if exists (
select 1
from old_teamtable
where team_id = (select top 1 team_id from inserted)
having count(*) = max(member_count)
and max(member_count) = min(member_count)
)

Answer 2

The following code demonstrates one way to manage a team history table based on inserts to a teams and users table. The trigger fires after each insert to TeamsAndUsers. For new teams, not already in the TeamHistory, appropriate rows are added and marked IsComplete = 0. The TeamHistory is then updated by checking all the teams affected by the insert to see if they have the correct number of users. If so, the IsComplete bit is set to 1 for the corresponding rows in the TeamHistory table.
-- Create sample tables.
create table TeamsAndUsers ( Id Int Identity, TeamId Int, UserId Int, TeamMembers Int );
create table TeamHistory ( Id Int Identity, TeamId Int, IsComplete Bit );
go
-- Create the trigger.
create trigger UpdateTeamHistory
on TeamsAndUsers
after Insert
as
set nocount on
-- Handle any teams we've not heard of before.
insert into TeamHistory ( TeamId, IsComplete )
select distinct TeamId, 0
from inserted
where TeamId not in ( select TeamId from TeamHistory );
-- See if any teams have been completed, i.e. all of their members are present.
update TeamHistory
set IsComplete = 1
where TeamId in (
select TAU.TeamId from (
-- TeamId values touched by the INSERT ...
select distinct TeamId from inserted ) as i inner join
-- ... matched with corresponding incomplete teams in the team history ...
TeamHistory as TH on TH.TeamId = i.TeamId and TH.IsComplete = 0 inner join
-- ... matched with users currently assigned to the teams.
TeamsAndUsers as TAU on TAU.TeamId = i.TeamId
group by TAU.TeamId
having Count( TAU.UserId ) = Max( TAU.TeamMembers ) );
go
-- Test the trigger.
insert into TeamsAndUsers ( TeamId, UserId, TeamMembers ) values
( 101, 1, 3 ), ( 101, 2, 3 );
select * from TeamsAndUsers;
select * from TeamHistory;
insert into TeamsAndUsers ( TeamId, UserId, TeamMembers ) values
( 101, 3, 3 );
select * from TeamsAndUsers;
select * from TeamHistory;
insert into TeamsAndUsers ( TeamId, UserId, TeamMembers ) values
( 102, 4, 1 );
select * from TeamsAndUsers;
select * from TeamHistory;
insert into TeamsAndUsers ( TeamId, UserId, TeamMembers ) values
( 103, 10, 2 );
select * from TeamsAndUsers;
select * from TeamHistory;
insert into TeamsAndUsers ( TeamId, UserId, TeamMembers ) values
( 103, 11, 2 );
select * from TeamsAndUsers;
select * from TeamHistory;
Aside: The select in the update looks rather clumsy, but it's late here. It can probably be tidied up a little.