Checking if a SQL Server login already exists

Question

I need to check if a specific login already exists on the SQL Server, and if it doesn\'t, then I need to add it.

I have found the following code to actually add the

Answer 1

In order to hande naming conflict between logins, roles, users etc. you should check the type column according to Microsoft sys.database_principals documentation

In order to handle special chacters in usernames etc, use N'' and [] accordingly.

Create login

USE MASTER
IF NOT EXISTS (SELECT 1 FROM master.sys.server_principals WHERE 
[name] = N'' and [type] IN ('C','E', 'G', 'K', 'S', 'U'))
    CREATE LOGIN [] 

Create database user

USE []
IF NOT EXISTS (SELECT 1 FROM sys.database_principals WHERE 
[name] = N'' and [type] IN ('C','E', 'G', 'K', 'S', 'U'))
    CREATE USER [] FOR LOGIN []

Create database role

USE []
IF NOT EXISTS (SELECT 1 FROM sys.database_principals WHERE 
[name] = N'' and Type = 'R')
    CREATE ROLE []

Add user to role

USE []
EXEC sp_addrolemember N'', N''

Grant rights to role

USE []
GRANT SELECT ON [] TO []
GRANT UPDATE ON [] ([]) TO []
GRANT EXECUTE ON [] TO []

The SQL is tested on SQL Server 2005, 2008, 2008 R2, 2014, 2016, 2017, 2019