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 login to the database, but I want to wrap this in an IF statement (somehow) to check if the login exists first.

CREATE LOGIN [myUsername] WITH PASSWORD=N'myPassword', 
DEFAULT_LANGUAGE=[us_english], 
CHECK_EXPIRATION=OFF, 
CHECK_POLICY=OFF 
GO

I understand that I need to interrogate a system database, but not sure where to start!

Answer 1

Here's a way to do this in SQL Server 2005 and later without using the deprecated syslogins view:

IF NOT EXISTS 
    (SELECT name  
     FROM master.sys.server_principals
     WHERE name = 'LoginName')
BEGIN
    CREATE LOGIN [LoginName] WITH PASSWORD = N'password'
END

The server_principals view is used instead of sql_logins because the latter doesn't list Windows logins.

If you need to check for the existence of a user in a particular database before creating them, then you can do this:

USE your_db_name

IF NOT EXISTS
    (SELECT name
     FROM sys.database_principals
     WHERE name = 'Bob')
BEGIN
    CREATE USER [Bob] FOR LOGIN [Bob] 
END

Answer 2

From here

If not Exists (select loginname from master.dbo.syslogins 
    where name = @loginName and dbname = 'PUBS')
Begin
    Select @SqlStatement = 'CREATE LOGIN ' + QUOTENAME(@loginName) + ' 
    FROM WINDOWS WITH DEFAULT_DATABASE=[PUBS], DEFAULT_LANGUAGE=[us_english]')

    EXEC sp_executesql @SqlStatement
End

Answer 3

As a minor addition to this thread, in general you want to avoid using the views that begin with sys.sys* as Microsoft is only including them for backwards compatibility. For your code, you should probably use sys.server_principals. This is assuming you are using SQL 2005 or greater.

Answer 4

You can use the built-in function:

SUSER_ID ( [ 'myUsername' ] )

via

IF [value] IS NULL [statement]

like:

IF SUSER_ID (N'myUsername') IS NULL
CREATE LOGIN [myUsername] WITH PASSWORD=N'myPassword', 
DEFAULT_LANGUAGE=[us_english], 
CHECK_EXPIRATION=OFF, 
CHECK_POLICY=OFF 
GO

https://technet.microsoft.com/en-us/library/ms176042(v=sql.110).aspx

Answer 5

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'<name>' and [<name>] accordingly.

Create login

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

Create database user

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

Create database role

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

Add user to role

USE [<databasename>]
EXEC sp_addrolemember N'<rolename>', N'<username>'

Grant rights to role

USE [<databasename>]
GRANT SELECT ON [<tablename>] TO [<rolename>]
GRANT UPDATE ON [<tablename>] ([<columnname>]) TO [<rolename>]
GRANT EXECUTE ON [<procedurename>] TO [<rolename>]

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

Answer 6

Try this (replace 'user' with the actual login name):

IF NOT EXISTS(
SELECT name 
FROM [master].[sys].[syslogins]
WHERE NAME = 'user')

BEGIN 
    --create login here
END

Answer 7

This is for Azure SQL:

IF (EXISTS(SELECT TOP 1 1 FROM sys.sql_logins WHERE [name] = '<login>'))
    DROP LOGIN [<login>];

Source: How to check whether database user already exists in Azure SQL Database

Answer 8

This works on SQL Server 2000.

use master
select count(*) From sysxlogins WHERE NAME = 'myUsername'

on SQL 2005, change the 2nd line to

select count(*) From syslogins WHERE NAME = 'myUsername'

I'm not sure about SQL 2008, but I'm guessing that it will be the same as SQL 2005 and if not, this should give you an idea of where t start looking.

Answer 9

what are you exactly want check for login or user ? a login is created on server level and a user is created at database level so a login is unique in server

also a user is created against a login, a user without login is an orphaned user and is not useful as u cant carry out sql server login without a login

maybe u need this

check for login

select 'X' from master.dbo.syslogins where loginname=<username>

the above query return 'X' if login exists else return null

then create a login

CREATE LOGIN <username> with PASSWORD=<password>

this creates a login in sql server .but it accepts only strong passwords

create a user in each database you want to for login as

CREATE USER <username> for login <username>

assign execute rights to user

 GRANT EXECUTE TO <username>

YOU MUST HAVE SYSADMIN permissions or say 'sa' for short

you can write a sql procedure for that on a database

create proc createuser
(
@username varchar(50),
@password varchar(50)
)
as
begin
if not exists(select 'X' from master.dbo.syslogins where loginname=@username)
begin
 if not exists(select 'X' from sysusers where name=@username)
 begin
exec('CREATE LOGIN '+@username+' WITH PASSWORD='''+@password+'''')
exec('CREATE USER '+@username+' FOR LOGIN '+@username)
exec('GRANT EXECUTE TO '+@username)
end
end
end

Answer 10

Starting SQL 2016:

DROP USER IF EXISTS [userName]

CREATE USER [userName] FOR LOGIN [loginName]

Answer 11

First you have to check login existence using syslogins view:

IF NOT EXISTS 
    (SELECT name  
     FROM master.sys.server_principals
     WHERE name = 'YourLoginName')
BEGIN
    CREATE LOGIN [YourLoginName] WITH PASSWORD = N'password'
END

Then you have to check your database existence:

USE your_dbname

IF NOT EXISTS
    (SELECT name
     FROM sys.database_principals
     WHERE name = 'your_dbname')
BEGIN
    CREATE USER [your_dbname] FOR LOGIN [YourLoginName] 
END