SET @start_value = @@global.general_log_file; SELECT @start_value; @start_value test.log '#---------------------FN_DYNVARS_004_01-------------------------#' SET @@global.general_log_file = DEFAULT; SET @a=concat(left(@@hostname, instr(concat(@@hostname, '.'), '.')-1), '.log'); SELECT RIGHT(@@global.general_log_file, length(@a)) = @a; RIGHT(@@global.general_log_file, length(@a)) = @a 1 '#--------------------FN_DYNVARS_004_02------------------------#' SET @@global.general_log_file = mytest.log; ERROR 42000: Incorrect argument type to variable 'general_log_file' SET @@global.general_log_file = 12; ERROR 42000: Incorrect argument type to variable 'general_log_file' '#----------------------FN_DYNVARS_004_03------------------------#' SELECT @@global.general_log_file = VARIABLE_VALUE FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES WHERE VARIABLE_NAME='general_log_file'; @@global.general_log_file = VARIABLE_VALUE 1 SET @@global.general_log_file= @start_value;