用mysql的存储过程实现生成唯一订单号

DELIMITER $$

USE `roamerbuddy`$$

DROP PROCEDURE IF EXISTS `generate_orderNo`$$

CREATE DEFINER=`root`@`%` PROCEDURE `generate_orderNo`(
  IN orderNamePre CHAR(4),
  IN num INT,
  OUT newOrderNo VARCHAR (25)
)
BEGIN
  -- 订单变化的值
  DECLARE orderNameValue INT ;
  -- 更新行数
  DECLARE updateRow INT ;
  -- 当前日期,有可能包含时分秒  
  DECLARE currentTime DATETIME ;
  -- 订单号   
  DECLARE orderCode VARCHAR (64) ;
  DECLARE orderNum INT DEFAULT 5; -- 订单变化的值
  -- 异常处理
  DECLARE CONTINUE HANDLER FOR 1062
  SET currentTime = NOW() ;
  
  -- 获得订单号
  SELECT 
    IFNULL(gs.ordervalue, 0) INTO orderNameValue 
  FROM
    generate_serialno gs 
  WHERE id = 1 ;
  
  SET currentTime = NOW() ;
  -- 打开自动提交
  SET autocommit = 1 ;
  IF TRUE -- 如果true插入一条数据
  THEN 
  INSERT INTO generate_serialno (id, ordervalue, ordertime) 
  VALUES
    (1, 1, currentTime) ;
  END IF ; -- 否则更改订单号
  UPDATE 
    generate_serialno obj 
  SET
    obj.ordervalue = 
    CASE -- 订单变化的值如果今天大于昨天从1开始，否则再原来的基础上加1
      WHEN TO_DAYS(currentTime) > TO_DAYS(obj.ordertime) 
      THEN 1 
      ELSE orderNameValue + 1 
    END,
    obj.ordertime = currentTime 
  WHERE ( -- 订单变化的值
      obj.id = 1 
      AND obj.ordervalue = orderNameValue
    ) ;
  SET updateRow = ROW_COUNT() ;
  
  WHILE
    ! updateRow = 1 DO -- 如果更改的行数不等于1
    SELECT -- 获得当前的订单变化值
      IFNULL(gs.ordervalue, 0) INTO orderNameValue 
    FROM
      generate_serialno gs 
    WHERE id = 1 ;
    
    UPDATE 
      generate_serialno obj 
    SET
      obj.ordervalue = 
      CASE
        WHEN TO_DAYS(currentTime) > TO_DAYS(obj.ordertime) 
        THEN 1 
        ELSE orderNameValue + 1 
      END,
      obj.ordertime = currentTime 
    WHERE (-- 只有订单变化值和id都相等的情况下才能更改，更具行锁的机制
        obj.id = 1 
        AND obj.ordervalue = orderNameValue  -- 注意！！！！
      ) ;
    SET updateRow = ROW_COUNT() ;
  END WHILE ;
  
  
  IF num = 8 
  THEN -- 根据年月日生成订单编号,订单编号形式:前缀+年月日+流水号，如：SH2013011000002     
  SELECT 
    CONCAT(
	  orderNamePre,
      DATE_FORMAT(currentTime, '%Y%m%d'),
      LPAD(orderNameValue, orderNum, '0')
    ) INTO orderCode ;
  ELSEIF num = 14 
  THEN -- 根据年月日时分秒生成订单编号,订单编号形式：前缀+年月日时分秒+流水号，如：SH2013011010050700001,个人不推荐使用这种方法生成流水号     
  SELECT 
    CONCAT(
	  orderNamePre,
      DATE_FORMAT(currentTime, '%Y%m%d%H%i%s'),
      LPAD(orderNameValue, orderNum, '0')
    ) INTO orderCode ;
  ELSE -- 根据年月日时分生成订单编号,订单形式：前缀+年月日时分+流水号,如：SH20130110100900005
  SELECT 
    CONCAT(
	  orderNamePre,
      DATE_FORMAT(currentTime, '%Y%m%d%H%i'),
      LPAD(orderNameValue, orderNum, '0')
    ) INTO orderCode ;
  END IF ;
  SELECT 
    orderCode ;
END$$

DELIMITER ;