Variables in SQL injection

@@hostname   ==>  Current Hostname
@@tmpdir         ==>  Tept Directory
@@datadir        ==> Data Directory
@@version        ==> Version of Data Base
@@basedir        ==> Base Directory
user()               ==>  Current User
database()       ==> Current Database
version()          ==>  Version
schema()         ==>   Current Database
UUID()             ==>   System UUID key
system_user()==>   Current system user
session_user()==>  Session user
@@Global.have_symlink==>Check if Symlink Enabled or Disabled
@@Global.have_ssl==>Check if it have ssl or not