How to See Active SQL Server Connections

How do I see active SQL Server connections?

You can use the sp_who stored procedure.

Provides information about current users, sessions, and processes in an instance of the Microsoft SQL Server Database Engine. The information can be filtered to return only those processes that are not idle, that belong to a specific user, or that belong to a specific session.

How to determine total number of open/active connections in ms sql server 2005

This shows the number of connections per each DB:

SELECT 
    DB_NAME(dbid) as DBName, 
    COUNT(dbid) as NumberOfConnections,
    loginame as LoginName
FROM
    sys.sysprocesses
WHERE 
    dbid > 0
GROUP BY 
    dbid, loginame

And this gives the total:

SELECT 
    COUNT(dbid) as TotalConnections
FROM
    sys.sysprocesses
WHERE 
    dbid > 0

If you need more detail, run:

sp_who2 'Active'

Note: The SQL Server account used needs the 'sysadmin' role (otherwise it will just show a single row and a count of 1 as the result)

How to get detailed list of connections to database in sql server 2005?

Use the system stored procedure sp_who2.

How to list opened sql server connections and close the specific one

For Listing:

select *
from sys.dm_exec_sessions

For Killing specific connection by id:

declare @session_id     int;
set          @session_id= ''

select 
    @session_id=cast(req.session_id as int) from sys.dm_exec_requests req where req.command='DbccSpaceReclaim'group by req.session_id

begin

declare @sql nvarchar(1000)
select @sql = 'kill ' +  cast(@session_id  as varchar(50))
 exec sp_executesql  @sql
end

How to list active connections on PostgreSQL?

Oh, I just found that command on PostgreSQL forum:

SELECT * FROM pg_stat_activity;

How to see opened connections /running queries in SQL Server 2008?

From the DMVs:

sys.dm_exec_connections
sys.dm_exec_sessions
sys.dm_exec_request
sys.dm_exec_sql_text

Additionally:

from the Activity Monitor
from SQL Profiler
from sp_whoIsActive