--source include/have_debug.inc # # exists both as global and session # set session debug_dbug="L"; select @@global.debug_dbug="1"; # just to show that global.debug_dbug exists select @@session.debug_dbug; # here we know the value and can display it --replace_column 2 # show global variables like 'debug_dbug'; show session variables like 'debug_dbug'; --replace_column 2 # select * from information_schema.global_variables where variable_name='debug_dbug'; select * from information_schema.session_variables where variable_name='debug_dbug'; --error ER_WRONG_TYPE_FOR_VAR set @@global.debug_dbug=1; --error ER_WRONG_TYPE_FOR_VAR set @@global.debug_dbug=1.1; --error ER_WRONG_TYPE_FOR_VAR set @@global.debug_dbug=1e1;