MySQL can repeatedly add columns

DROP PROCEDURE IF EXISTS ' add_column_if '; CREATE PROCEDURE ' add_column_if ' (in v_table varchar ( -), in V_column varchar ( -), in v_discription varchar ( +)) BEGIN DECLARE stmt varchar ( -); DECLARE V_flagint; SelectCOUNT (*) into V_flag fromInformation_schema.columnswhereTable_schema = (SelectDATABASE ()) and table_name = v_table and COLUMN_NAME =V_column; if(v_flag=0) ThenSet@sqlstr = Concat ('ALTER TABLE '', V_table,'' ADD COLUMN '', V_column,'` ', v_discription); Prepare stmt from@sqlstr;    Execute stmt; Endif; Commit;end;

Call:

Call add_column_if ('xxx','xxx',' XXX ');

MySQL can repeatedly add columns