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Difference between a User and a Login in SQL Server
Is it enough to create a database login with permission to desired database? Or do I need to create a database user for this login?
A login is a login account for the entire SQL Server instance - an instance can contain numerous databases.
A user is defined at the database level, and is associated with a login to provide interactive access (privileges providing)
Logins are a server side (instance level) objects. Their correct name is 'server principals' (see sys.server_principals). Server wide privileges are granted to logins, like create database or view server state permissions.
Users are a database objects, correctly referred to as 'database principals' (see sys.database_principals). They are the recipients of database permissions, like create table or select.
Ordinarily a login is mapped 1-to-1 to a user in each database, via a matching SID, but there are some exception, like all members of the sysadmin fixed server role are always mapped to dbo.
Users without login are a specific construct for Service Broker remote identities (see Remote Service Bindings) and for code signing. You should never have to create one in any other context, and if you do, you're likely doing it wrong. Users without login are never meant to be impersonated.
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Disclosure: I am not an IT professional and I am certainly not a DBA.
That said, I can usually find my way around. I am following some instructions from a third party vendor to create a login, two databases, a user in each and ultimately a DSN to each.
Here are the steps:
Create a login (let's call it Test) with SQL Server Authentication and assign it a Public server role
Create two databases, both owned by the login we created (Test)
In each database, create a user with User Name and Login Name both set to Test and the default schema as dbo. Assign each user db_owner in Owned Schemas and Membership
Create a DSN to each database
If I follow these instructions, when I attempt to create the users I get an error: The login already has an account under a different user name. (Microsoft SQL Server, Error: 15063)
If I try creating a user with a different User Name (login name still Test), I get the same error.
If I try creating a user with a different Login Name, I get a different error: 'Test1' is not a valid login or you do not have permission. (Microsoft SQL Server, Error: 15007)
If I try skipping the users entirely and creating the DSN with the original Login, I get an error that login failed for user Test.
I have tried completely removing and re-installing SQL Server in case there was some duplicate name stored somewhere, but it didn't help.
So, I am not sure what else I can try. Clearly I am missing something, but I have no idea what.
If the Login owns the database, it's mapped to the user dbo (which stands for "database owner") so you can't create another user for that login.
Normal practice is to have the databases owned by SA or your Windows Login, then you can create the user for the SQL Login and assign whatever permissions you need.
I have got myself into a little bit of a bind, using SQL Server Management Studio to create a database in Azure SQL. My issue appears to be with assigning roles to users in the database. When I created the database, it prompted me to create a new login, with an associated user, that appeared to have all the rights of a database owner. However, I am now trying to create two additional logins and I realize I am screwed. The login that I created when I made the database isn't the database owner, even though I could do all the DDL / DML necessary to create the full schema under that account. I created an additional login, and I added two users to that login. I now want to add that login to a role (db_datareader, db_denywrite) but I cannot.
It appears that the database owner is a user / login called "dbo" that I did not set up. This is the only user that is added as a database owner, and subsequently is the only one that can edit roles. But I do not know the login credentials for this user!
if I use what I believed to be the administrator account (the one I made) to add a role I get the error:
Cannot alter the role 'db_datareader', because it does not exist or you do not have permission.
How can I fix this? How can I get my original account added as a DB Owner? There has got to be a way, but everything I tried points to the fact that I am not the owner of the resource I created; I'm an outcast in my own country...
Thanks!
I have a Microsoft SQL server database and a set of users.
Now in my app I want to make some functionality only visible, if the user has entered username and password with certain rights (admin).
Since the databases and the usernames and their rights can change, how do i check what permissions/rights an Microsoft SQL server user has?
You can check current user's right on certain securables using [sys.fn_mypermissions][1] which returns all permission on the securable. You can also check a specific permission with HAS_PERMS_BY_NAME. Eg. you can check for CONTROL SERVER permission which implies an administrator is logged in:
SELECT HAS_PERMS_BY_NAME(null, null, 'CONTROL SERVER');
The simplest way to do this is using the IS_MEMBER('rolename') function, that checks whether the user is in the role/group 'db_owner'. The function will perform a check at database level, and returns 1 (Int32), if the user has the specified role.
If you need to check at server level, you can use the IS_SRVROLEMEMBER function. Both are available since SQL Server 2005.
I'm not entirely certain that I understand your problem definition however assuming I do.....
I would suggest that you create a SQL Server Database Role that you can add the relevant application users to, perhaps via some group membership maintained within the App (or a Windows Domain Group). You can use the group to Role mapping to independently manage user membership, from managing the relevant permissions to securables within the database via the Role.
This way, you just need to check that an application User is a member of the relevant application or windows group, without the need to query the security configuration of SQL Server.
I'm quite new to Microsoft SQL Server. I have some experience with MySQL, and there you have a user with privileges, if I understand things right; these privileges decide which databases you have access to on the MySQL server.
However now I am in the situation where I have to restore a database on my SQL Server 2005 Express, and this database has it's own users and user password. So if I want to make these users accessible from the outside (so that they can connect to my server), how would I go about that?
To illustrate clearer; say there are two login accounts on the database server "Mike" and "John", and on the database "Animals" there are two users; "Chris" and "Jeff".
I need Jeff to be able to sign in to get access to the database. Is there a good way to make this happen without creating new users/logins? And if not, what is the best/most common solution?
I would really appreciate any helpful input on this!
One server-level object (login) is mapped to multiple database-level objects (users).
A login cannot be mapped to more than one user within a database, but can be mapped to at most one user in each database.
Therefore, you need to create new logins for those users, but map them to existing users. This is done with ALTER USER command. Or, if you don't have any use for the Mike and John logins apart from mapping them to those existing users, you can do so, too.
Any user needing to access a database needs to either have their own login, or you can create a login for a Windows security group and grant access that way to a whole set of users. Then if you need to give access to more users in the future you can just add them to the windows security group.
I have recently been running into many different areas of SQL Server that I normally don't mess with. One of them that has me confused is the area of Logins and Users. Seems like it should be a pretty simple topic...
It appears that each login can only have 1 user and each user can only have 1 login.
A login can be associated to multiple tables thus associating that user to many tables.
So my question is why even have a login and a user? they seem to be pretty much one in the same. What are the differences, or what is it that I seem to be missing?
A "Login" grants the principal entry into the SERVER.
A "User" grants a login entry into a single DATABASE.
One "Login" can be associated with many users (one per database).
Each of the above objects can have permissions granted to it at its own level. See the following articles for an explanation of each
Principals
Database Users
One reason to have both is so that authentication can be done by the database server, but authorization can be scoped to the database. That way, if you move your database to another server, you can always remap the user-login relationship on the database server, but your database doesn't have to change.
I think there is a really good MSDN blog post about this topic by Laurentiu Cristofor:
The first important thing that needs to be understood about SQL Server
security is that there are two security realms involved - the server
and the database. The server realm encompasses multiple database
realms. All work is done in the context of some database, but to get
to do the work, one needs to first have access to the server and then
to have access to the database.
Access to the server is granted via logins. There are two main
categories of logins: SQL Server authenticated logins and Windows
authenticated logins. I will usually refer to these using the shorter
names of SQL logins and Windows logins. Windows authenticated logins
can either be logins mapped to Windows users or logins mapped to
Windows groups. So, to be able to connect to the server, one must have
access via one of these types or logins - logins provide access to the
server realm.
But logins are not enough, because work is usually done in a database
and databases are separate realms. Access to databases is granted via
users.
Users are mapped to logins and the mapping is expressed by the SID
property of logins and users. A login maps to a user in a database if
their SID values are identical. Depending on the type of login, we can
therefore have a categorization of users that mimics the above
categorization for logins; so, we have SQL users and Windows users and
the latter category consists of users mapped to Windows user logins
and of users mapped to Windows group logins.
Let's take a step back for a quick overview: a login provides access
to the server and to further get access to a database, a user mapped
to the login must exist in the database.
that's the link to the full post.
In Short,
Logins will have the access of the server.
and
Users will have the access of the database.
I think this is a very useful question with good answer. Just to add my two cents from the MSDN Create a Login page:
A login is a security principal, or an entity that can be authenticated by a secure system. Users need a login to connect to SQL Server. You can create a login based on a Windows principal (such as a domain user or a Windows domain group) or you can create a login that is not based on a Windows principal (such as an SQL Server login).
Note:
To use SQL Server Authentication, the Database Engine must use mixed mode authentication. For more information, see Choose an Authentication Mode.
As a security principal, permissions can be granted to logins. The scope of a login is the whole Database Engine. To connect to a specific database on the instance of SQL Server, a login must be mapped to a database user. Permissions inside the database are granted and denied to the database user, not the login. Permissions that have the scope of the whole instance of SQL Server (for example, the CREATE ENDPOINT permission) can be granted to a login.
Graph on logins / users from MS sql-docs