SQL Server

Have you ever needed to write a script that would store the Windows login of the user that executes the script in a table, without hard-coding it?  And you couldn’t find your way through the user jungle of T-SQL?  Then read on!

A normal approach would be to rely on the IntelliSense feature of SSMS and start typing something like:

select use

Which gives you a dropdown like:

Cool you think, there are four system functions to return something user-related, one of them would be the Windows user, right?  Well, wrong.

Let’s find out what these functions actually return, and locate a method that does return what we require.

The Different User-Related System Functions

USER

According to the BOL:

Allows a system-supplied value for the database user name of the current user to be inserted into a table when no default value is specified.

So, how many times did you read that?  And do you now know what you’ll get?  Me neither.  As far as I understand it, you’ll get the database user name of the connection context.  Not what we need.

USER_ID

According to BOL:

Returns the identification number for a database user.

The function accepts one argument that accepts a string representing a username.  When no argument is provided, it will return the user ID of the execution context.

But that’s not important because the BOL also mentions that it will be removed in a future version and that you thus shouldn’t use it anymore.  No problem if you need it though, its replacement is called DATABASE_PRINCIPAL_ID.

USER_NAME

According to BOL:

Returns a database user name from a specified identification number.

This is the inverse of USER_ID.  It accepts one argument representing the user ID.  When omitted, the user of the current execution context will be returned.  Which is actually the equivalent of the USER function.

Still no Windows user though, so let’s move on to the next one.

USER_SID

Not documented in the BOL.

It seems to represent the sid column found through following query:

select * from sys.sysusers

And the sys.sysusers view is documented.  Apparently “sid” stands for “security identifier” and it’s a varbinary.  But not only is the view documented, it is also deprecated.  You should use the following view instead:

select * from sys.database_principals

That query returns a list of principals in the current database, and one of the fields is indeed our dear sid.  However, we can now conclude that sid is definitely not what we’re looking for in this little quest, it doesn’t even closely resemble a Windows user name.  So let’s move on again!

CURRENT_USER

Hmm, “current user”, will this finally be the Windows user with which I’m running my queries?

According to BOL:

Returns the name of the current user. This function is equivalent to USER_NAME().

Equivalent to USER_NAME, so still not what we’re looking for.

SESSION_USER

According to BOL:

SESSION_USER returns the user name of the current context in the current database.

You can probably guess by now that again this is not what we’re searching for.  Next.

SYSTEM_USER

According to BOL:

Allows a system-supplied value for the current login to be inserted into a table when no default value is specified.

Ah, finally a description that contains the word “login”!  And indeed, here’s what it returns:

ORDINA\VaVr

That is indeed my Windows user.  Mission accomplished!

Please note: if you’re running this through a window connected via a SQL Server login, you will get that login as opposed to your Windows login.  And if you get ‘sa’ while you’re connected to a production server you should look into making some security changes.

SUSER_NAME and SUSER_SNAME

Two more similar functions exist: SUSER_NAME and SUSER_SNAME.

Both return a login name as well, and both accept a parameter.  When executed without parameter, they return the login name of the current user.  Their only difference is the parameter that they accept.  SUSER_NAME accepts the “login identification number of the user”, which is an int, and SUSER_SNAME accepts the “login security identification number”, a varbinary(85) (remember sid from above?).

Quick Query

The following query shows how to use all the functions, with the default values for any parameters.

select USER as cUSER, USER_ID() as cUSER_ID, USER_NAME() as USER_NAME,
    USER_SID() as cUSER_SID, CURRENT_USER as cCURRENT_USER,
    SESSION_USER as cSESSION_USER, SYSTEM_USER as cSYSTEM_USER,
    SUSER_NAME() as cSUSER_NAME, SUSER_SNAME() as cSUSER_SNAME

Have fun!