i am getting an issue with xlat

i tried this

sql sql2 {

}

sql sql_gowifi{
sql_user_name = "%{sql2:select s.* from (select @user:=BINARY '%{User-Name}' p) parm , upm s}"
}

and using sql_gowifi in sites-enabled/default for mysql based login and accounting

again when using sql_user_name = "%{User-Name}" it saves the username entered in login page of hotspot to radpostauth table but with the code above the username remains blank

when i run the sql query above in mysql server it returns the correct username please help