How to resolve SQL Server error 18456?

10 months ago

Noah Thompson

2 minutes

SQL Server error 18456 refers to a login failure error encountered when logging into SQL Server. This error is usually caused by a few common reasons.

Incorrect username or password: Please make sure that the username and password you entered are correct, especially when distinguishing between uppercase and lowercase letters.
SQL Server authentication mode is not enabled: Make sure that SQL Server authentication mode is enabled in SQL Server Configuration Manager. By default, SQL Server only enables Windows authentication mode.
The user does not have permission to login to SQL Server: Please check if the user has the necessary permissions to access the database. You can connect to the database through SQL Server Management Studio and then verify the permissions of the login user.
The login user is disabled: Please check if the login user is in a disabled state. You can connect to the database through SQL Server Management Studio and then check the status of the login user.

If the above methods do not work, you can try the following solutions:

Reset password: log in to SQL Server with user credentials that have sysadmin permission and proceed to reset the login user’s password.
Check the default database of the logged in user: Log in to SQL Server with a user account that has sysadmin permission, then verify if the default database for the logged in user exists.
Check the SQL Server error log: Open the SQL Server error log, search for detailed error information related to error 18456. Based on the error information, try to resolve the related issue.
Check the SQL Server authentication mode: make sure that the SQL Server authentication mode is enabled in SQL Server Configuration Manager.
Check SQL Server login user permissions: Make sure the login user has the necessary permissions to access the required database.

If the issue still cannot be resolved, it is advisable to consult the technical support team of SQL Server or seek the help of a professional database administrator.