mysql存儲過程，有輸入輸出的

mysql存儲過程，有輸入輸出的   Sql代碼   DELIMITER //;      CREATE  PROCEDURE queryTotalNum(OUT totalNum INT , IN tableName varchar(40), IN conditions varchar(300))   begin           declare stmt varchar(2000);          declare num int;       if LENGTH(conditions)>1 then         begin           set @sqlstr=concat('SELECT COUNT(*) INTO @num from ',tableName,' where ',conditions);       end;       else       begin            set @sqlstr=concat('SELECT COUNT(*) INTO @num from ',tableName);       end;       end if;         prepare stmt from @sqlstr;           execute stmt;         deallocate prepare stmt;       set totalNum = @num;          end;