Hi Vivek,
Here, in this case, it is expected error, not a bug.
USER_NAME function accepts INT(INTEGER) Datatype Values. INT range is [0 2147483647]
However "sysuser.user_id" Datatype is Insigned INT, thus could support values up to 4294967295.
Solution : Instead of query
select User_Name(sysuser.user_id) from sysuser ;
Use query
select user_name from sysuser ;
No need to use function User_Name. Column "sysuser.user_name" can be used.
When you need aboslutedly to use USER_NAME function, make sure the parameter is in range [0-2147483647]. Eg. select user_name(sysuser.user_id) from sysuser where user_id <=2147483647 and ....
For uper values user "sysuser.user_name" column
Regards,
Tayeb.