Cannot insert the value NULL into column I have a script for scripting out user permissions I use on SQL 2014 that works fine but when I try on SQL 2008, I am getting the following error:

Msg 515, Level 16, State 2, Line 4
Cannot insert the value NULL into column 'UserName', table '@DB_USers'; column does not allow nulls. INSERT fails.
The statement has been terminated.

(0 row(s) affected)

DECLARE @DB_USers TABLE
(DBName sysname, UserName sysname, LoginType sysname, AssociatedRole varchar(max),create_date datetime,modify_date datetime)

INSERT @DB_USers
EXEC sp_MSforeachdb

'
use [?]
SELECT ''?'' AS DB_Name,
case prin.name when ''dbo'' then prin.name + '' (''+ (select SUSER_SNAME(owner_sid) from master.sys.databases where name =''?'') + '')'' else prin.name end AS UserName,
prin.type_desc AS LoginType,
isnull(USER_NAME(mem.role_principal_id),'''') AS AssociatedRole ,create_date,modify_date
FROM sys.database_principals prin
LEFT OUTER JOIN sys.database_role_members mem ON prin.principal_id=mem.member_principal_id
WHERE prin.sid IS NOT NULL and prin.sid NOT IN (0x00) and
prin.is_fixed_role &lt;&gt; 1 AND prin.name NOT LIKE ''##%'''

SELECT

dbname,username ,logintype ,create_date ,modify_date ,

STUFF(

(

SELECT ',' + CONVERT(VARCHAR(500),associatedrole)

FROM @DB_USers user2

WHERE

user1.DBName=user2.DBName AND user1.UserName=user2.UserName

FOR XML PATH('')

)

,1,1,'') AS Permissions_user

FROM @DB_USers user1

GROUP BY

dbname,username ,logintype ,create_date ,modify_date

ORDER BY DBName,username
I didn't take a really hard look at this but you're defining the DBName, UserName, and LoginType columns in @DB_USers as sysname. The type sysname is defined as NOT NULL.

What is SYSNAME data type in SQL Server? 

As to why you're getting a NULL value you're going to have to check the dataset you're running against.