Find orphaned users

The following script from the Brent Ozar Unlimited site iterates through all databases and lists the orphaned users by database, along with the drop command to remove them. There may be a neater/newer way of handling this but this appears to function correctly on 2005-2012.

DECLARE @SQL nvarchar(2000)
DECLARE @name nvarchar(128)
DECLARE @database_id int

SET NOCOUNT ON;

IF NOT EXISTS 
    (SELECT name FROM tempdb.sys.tables WHERE name like '%#orphan_users%')
BEGIN
    CREATE TABLE #orphan_users
        (
        database_name nvarchar(128) NOT NULL,
        [user_name] nvarchar(128) NOT NULL,
        drop_command_text nvarchar(200) NOT NULL
        )
END

CREATE TABLE #databases 
(
    database_id int NOT NULL
    , database_name nvarchar(128) NOT NULL
    , processed bit NOT NULL
)

INSERT
    #databases 
    ( database_id
    , database_name
    , processed )
SELECT 
    database_id
    , name
    , 0 
FROM 
    master.sys.databases 
WHERE 
    name NOT IN 
    ('master'
    , 'tempdb'
    , 'msdb'
    , 'distribution'
    , 'model')

WHILE (SELECT COUNT(processed) FROM #databases WHERE processed = 0) > 0
BEGIN
    SELECT TOP 1
        @name = database_name,
        @database_id = database_id
    FROM #databases
    WHERE processed = 0
    ORDER BY database_id

    SELECT @SQL =

'USE [' + @name + '];
INSERT INTO #orphan_users (database_name, user_name, drop_command_text)
SELECT 
    DB_NAME()
    , u.name
    , ' + '''' 
    + 'USE [' + @name + ']; ' 
    + 'DROP USER [' 
    + '''' + ' + u.name 
    + ' + '''' + '] ' 
    + '''' + '
FROM
    master..syslogins l
RIGHT JOIN 
    sysusers u 
ON l.sid = u.sid
WHERE   
    l.sid IS NULL
AND issqlrole <> 1
AND isapprole <> 1
AND ( u.name <> ' + '''' + 'INFORMATION_SCHEMA' + ''''
        + ' AND u.name <> ' + '''' + 'guest' + ''''
        + ' AND u.name <> ' + '''' + 'dbo' + ''''
        + ' AND u.name <> ' + '''' + 'sys' + ''''
        + ' AND u.name <> ' + '''' + 'system_function_schema' + '''' + ')'

    PRINT @SQL;

    EXEC sys.sp_executesql @SQL

    UPDATE 
        #databases 
    SET 
        processed = 1 
    WHERE 
        database_id = @database_id;
END

SELECT 
    database_name
    , [user_name]
    , drop_command_text 
FROM 
    #orphan_users 
ORDER BY 
    [database_name]
    , [user_name];

DROP TABLE #databases;
DROP TABLE #orphan_users;

SET NOCOUNT OFF;

I wanted to first THANK Mark for posting the script. It saved me a bunch of time writing it from scratch. I modified it a little bit since I ran into the issue where i received an error stating the "database principal owns a schema in the database, and cannot be dropped" error. I modified the script to generate the commands for the SCHEMA error and also for the Role error if you should get that one as well.

Hope this helps someone out there..

DECLARE @SQL nvarchar(2000)
DECLARE @name nvarchar(128)
DECLARE @database_id int

SET NOCOUNT ON;

IF NOT EXISTS 
    (SELECT name FROM tempdb.sys.tables WHERE name like '%#orphan_users%')
BEGIN
    CREATE TABLE #orphan_users
        (
        database_name nvarchar(128) NOT NULL,
        [user_name] nvarchar(128) NOT NULL,
        drop_command_text nvarchar(200) NOT NULL,
        drop_schema_text nvarchar(200) not null,
        drop_role_text nvarchar(200) not null
        )
END

CREATE TABLE #databases 
(
    database_id int NOT NULL
    , database_name nvarchar(128) NOT NULL
    , processed bit NOT NULL
)

INSERT
    #databases 
    ( database_id
    , database_name
    , processed )
SELECT 
    database_id
    , name
    , 0 
FROM 
    master.sys.databases 
WHERE 
    name NOT IN 
    ('master'
    , 'tempdb'
    , 'msdb'
    , 'distribution'
    , 'model')

WHILE (SELECT COUNT(processed) FROM #databases WHERE processed = 0) > 0
BEGIN
    SELECT TOP 1
        @name = database_name,
        @database_id = database_id
    FROM #databases
    WHERE processed = 0
    ORDER BY database_id

    SELECT @SQL =

'USE [' + @name + '];
INSERT INTO #orphan_users (database_name, user_name, drop_command_text, Drop_schema_text, drop_role_text)
SELECT 
    DB_NAME()
    , u.name
    , 
        ' + '''' 
        + 'USE [' + @name + ']; ' 
        + 'DROP USER [' 
        + '''' + ' + u.name 
        + ' + '''' + '] ' 
        + '''' + '
    , 
        ' + '''' + 'USE [' + @name + ']; ' +
        'ALTER AUTHORIZATION ON SCHEMA::[' 
        + '''' + ' + u.name 
        + ' + '''' + ']  TO [dbo]' + '''' + '
    , 
        ' + '''' + 'USE [' + @name + ']; ' +
        'ALTER AUTHORIZATION ON Role::[' 
        + '''' + ' + u.name 
        + ' + '''' + ']  TO [dbo]' + '''' + '
FROM
    master..syslogins l
RIGHT JOIN 
    sysusers u 
ON l.sid = u.sid
WHERE   
    l.sid IS NULL
AND issqlrole <> 1
AND isapprole <> 1
AND ( u.name <> ' + '''' + 'INFORMATION_SCHEMA' + ''''
        + ' AND u.name <> ' + '''' + 'guest' + ''''
        + ' AND u.name <> ' + '''' + 'dbo' + ''''
        + ' AND u.name <> ' + '''' + 'sys' + ''''
        + ' AND u.name <> ' + '''' + 'system_function_schema' + '''' + ')'

    PRINT @SQL;

    EXEC sys.sp_executesql @SQL

    UPDATE 
        #databases 
    SET 
        processed = 1 
    WHERE 
        database_id = @database_id;
END

SELECT 
    database_name
    , [user_name]
    , drop_command_text 
    , Drop_schema_text
    , drop_role_text
FROM 
    #orphan_users 
ORDER BY 
    [database_name]
    , [user_name];

DROP TABLE #databases;
DROP TABLE #orphan_users;

SET NOCOUNT OFF;

This sp_change_users_login is depreciated as of SQL 2008 but still works well. If you pass in the 'report' option then it will list all of the users that don't have an associated login.

EXEC sp_change_users_login 'report'

If you want to run it for all of your databases you can do it like this.

EXEC sp_msforeachdb 'use [?]; PRINT ''?''; EXEC sp_change_users_login ''report'';'

If you look it up in BOL you will also find options for fixing "orphaned" users.