占位符和exec动态执行
传入的code是传gcode
CREATE DEFINER=`root`@`localhost` PROCEDURE `studydata`.`test22`(IN code char(255))
READS SQL DATA
BEGIN
set @gcode = code;
set @ssra = concat('select * from acctmy where gcode in (?)');
PREPARE sqlquery FROM @ssra;
EXECUTE sqlquery USING @gcode;
END;