Mapping User Login and Database Roles to Existing User

Error:
User, group, or role 'xxx' already exists in the current database. (.Net SqlClient Data Provider)

Explanation:
This error happens when you try to add user mapping to the server logins using username which already exists in the database to be assigned.

In my case, the user exists in both server logins and database logins, but the user mapping and database roles on the server logins for this user cannot be modified although the user mapping is incorrect, because it already exists on the database logins.

Solution:
Run this script to update the user mapping accordingly.

USE <database_name>
EXEC sp_change_Users_login 'update_one', '<login_username>', '<login_username>'

This will update the user mapping and database roles on server logins to follow the ones on the database logins.

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Current Transaction Cannot be Committed

Error:
The current transaction cannot be committed and cannot support operations that write to the log file. Roll back the transaction.

This error occurs when you try to perform other operations when any transaction fails in try catch section, soon after it goes to catch section.

Solution:
You have to ROLLBACK first on the catch section before doing any other operations.

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Directory Lookup Failed on SQL Server

When executing script on SQL server, this error occurs:
Directory lookup for the file <filepath> failed with the operating system error 2(The system cannot find the file specified.)

Directory lookup for the file <filepath> failed with the operating system error 3(The system cannot find the path specified.)

Solution:
Check the directory used in the SQL script. Make sure that the directory used in the SQL script point to the server location, if the script is not directly executed from the server.

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