MySQL之简单示例

 

Create Table

1.创建数据表

• CREATE TABLE `amount` (
•   `id` int(11) NOT NULL AUTO_INCREMENT,
•   `amount` decimal(10,2) DEFAULT NULL,
•   PRIMARY KEY (`id`)
• ) ENGINE=InnoDB  DEFAULT CHARSET=utf8

DELIMITER $$

2.创建触发器示例
（1）CREATE
    /*[DEFINER = { user | CURRENT_USER }]*/
    TRIGGER `mytest`.`tri_amount2` BEFORE UPDATE
    ON `mytest`.`amount`
    FOR EACH ROW BEGIN
     IF (NEW.amount < 0) THEN
          SET NEW.amount = 0;tri_amount1
     ELSEIF (NEW.amount > 100) THEN
          SET NEW.amount = 100;
     END IF;
    
    END$$

DELIMITER ;

再插入时触发这个程序

 

（2）BEGIN
     IF (NEW.amount < 0) THEN
          SET NEW.amount = 0;
     ELSEIF (NEW.amount > 100) THEN
          SET NEW.amount = 100;
     END IF;
    
    END