在借阅表和读者表当中存在着这样的关系，如果在借阅表当中添加一条数据，读者表当中对应的累计借书字段就自增1，如果在借阅表当中删除一条数据，读者表当中对应的累计借书字段就自减1，实现本功能的方法如下。
1、创建读者表
1 CREATE TABLE `t_borrowbook` (
2 `borrowBookId` int(11) NOT NULL AUTO_INCREMENT,
3 `bookId` int(11) DEFAULT NULL,
4 `id` int(11) DEFAULT NULL,
5 `audienceId` int(11) DEFAULT NULL,
6 `startTime` datetime DEFAULT NULL,
7 `endTime` datetime DEFAULT NULL,
8 `borrowBookDesc` text,
9 PRIMARY KEY (`borrowBookId`)
10 )
2、创建借阅表
1 CREATE TABLE `t_audience` (
2 `audienceId` int(10) NOT NULL AUTO_INCREMENT,
3 `audienceName` varchar(20) NOT NULL,
4 `audienceTypeId` int(10) NOT NULL,
5 `audienceNumber` varchar(18) NOT NULL,
6 `sex` varchar(20) DEFAULT NULL,
7 `cellphone` varchar(11) DEFAULT NULL,
8 `borrowBookNum` int(10) DEFAULT NULL,
9 `audienceDesc` text,
10 PRIMARY KEY (`audienceId`)
11 )
3、创建插入自增触发器
1 DELIMITER $$
2
3 CREATE
4 /*[DEFINER = { user | CURRENT_USER }]*/
5 TRIGGER `db_book`.`Tr_borrowbook_Insert` AFTER INSERT
6 ON `db_book`.`t_borrowbook`
7 FOR EACH ROW BEGIN
8 UPDATE t_audience SET borrowBookNum = borrowBookNum+1 WHERE audienceId=new.audienceId;
9 END$$
10
11 DELIMITER ;
4、创建删除自减触发器
1 DELIMITER $$
2
3 CREATE
4 /*[DEFINER = { user | CURRENT_USER }]*/
5 TRIGGER `db_book`.`Tr_borrowbook_Delete` AFTER DELETE
6 ON `db_book`.`t_borrowbook`
7 FOR EACH ROW BEGIN
8 UPDATE t_audience SET borrowBookNum = borrowBookNum-1 WHERE audienceId=old.audienceId;
9 END$$
10
11 DELIMITER ;
每天进步一点点，一切都是最好的安排。