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Troubleshoot orphaned users (SQL Server)

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW)

Users are orphaned in SQL Server when a database user is based on a login in the master database but the login no longer exists in master. This can occur when the login is deleted or when the database is moved to another server on which the login doesn't exist. This article describes how to find orphaned users and remap them to logins.

Note

Reduce the possibility of orphaned users by using contained database users for databases that might be moved. For more information, see Make your database portable by using contained databases.

Background

For connections to a database on an instance of SQL Server that use a security principal (database user identity) based on a login, the principal must have a valid login in the master database. This login is used in the authentication process that verifies the principal's identity and determines whether the principal is allowed to connect to the instance of SQL Server. The SQL Server logins on a server instance are visible in the sys.server_principals catalog view and the sys.sql_logins compatibility view.

SQL Server logins access individual databases as a "database user" that's mapped to the SQL Server login. There are three exceptions to this rule:

  • Contained database users

    Contained database users authenticate at the user-database level and aren't associated with logins. This model is recommended because the databases are more portable, and contained database users can't become orphaned. However, they must be re-created for each database. This model might be impractical in an environment that has many databases.

  • The guest account

    When enabled in a database, this account permits SQL Server logins that aren't mapped to a database user to access the database as the guest user. The guest account is disabled by default.

  • Microsoft Windows group memberships

    A SQL Server login created from a Windows user can access a database if the Windows user is a member of a Windows group that's also a user in the database.

Information about the mapping of a SQL Server login to a database user is stored in the database. It includes the name of the database user and the security identifier (SID) of the corresponding SQL Server login. The permissions of this database user are applied for authorization in the database.

A database user (based on a login) for which the corresponding SQL Server login is undefined or is incorrectly defined on a server instance can't sign in to the instance. Such a user is said to be an orphaned user of the database on that server instance. Orphaning can happen if the database user is mapped to a login SID that's not present in the master database. A database user can become orphaned after a database is restored or attached to a different instance of SQL Server where the login was never created. A database user can also become orphaned if the corresponding SQL Server login is dropped. Even if the login is re-created, it will have a different SID, so the database user will still be orphaned.

Detect orphaned users

For SQL Server and PDW

To detect orphaned users in SQL Server based on missing SQL Server authentication logins, run the following statement in the user database:

SELECT dp.type_desc, dp.sid, dp.name AS user_name
FROM sys.database_principals AS dp
LEFT JOIN sys.server_principals AS sp
    ON dp.sid = sp.sid
WHERE sp.sid IS NULL
    AND dp.authentication_type_desc = 'INSTANCE';

The output lists the SQL Server authentication users and corresponding SIDs in the current database that aren't linked to any SQL Server login.

For Azure SQL Database and Azure Synapse Analytics

The sys.server_principals table isn't available in SQL Database or Azure Synapse Analytics. Identify orphaned users in those environments by completing these steps:

  1. Connect to the master database and select the SIDs for the logins by using the following query:

    SELECT sid
FROM sys.sql_logins
WHERE type = 'S';

  2. Connect to the user database and review the SIDs of the users in the sys.database_principals table by using the following query:

    SELECT name, sid, principal_id
FROM sys.database_principals
WHERE type = 'S'
  AND name NOT IN ('guest', 'INFORMATION_SCHEMA', 'sys')
  AND authentication_type_desc = 'INSTANCE';

  3. Compare the two lists to determine whether there are user SIDs in the user database sys.database_principals table that aren't matched by login SIDs in the master database sql_logins table.

Resolve an orphaned user

In the master database, use the CREATE LOGIN statement with the SID option to re-create a missing login. Provide the SID of the database user that you obtained in the previous section.

CREATE LOGIN <login_name>
WITH PASSWORD = '<use_a_strong_password_here>',
SID = <SID>;

To map an orphaned user to a login that already exists in master, run the ALTER USER statement in the user database, specifying the login name:

ALTER USER <user_name> WITH Login = <login_name>;

When you re-create a missing login, the user can access the database by using the password provided. The user can then change the password of the login account by using the ALTER LOGIN statement:

ALTER LOGIN <login_name> WITH PASSWORD = '<enterStrongPasswordHere>';

Important

Any login can change its own password. Only logins with the ALTER ANY LOGIN permission can change the password of another user's login. However, only members of the sysadmin role can modify passwords of sysadmin role members.

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