Java SSM框架之MyBatis3（八）MyBatis之动态SQL

前言：

　　mybatis框架中最具特色的便是sql语句中的自定义，而动态sql的使用又使整个框架更加灵活。

创建User表

/*Table structure for table `user` */

DROP TABLE IF EXISTS `user`;

CREATE TABLE `user` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  `username` varchar(20) NOT NULL,
  `age` int(3) NOT NULL,
  `phone` varchar(11) NOT NULL,
  `email` varchar(50) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

/*Data for the table `user` */

insert  into `user`(`id`,`name`,`username`,`age`,`phone`,`email`) values (1,‘张三‘,‘zs‘,18,‘15010998046‘,‘[email protected]‘),(2,‘李四‘,‘ls‘,19,‘15019087600‘,‘[email protected]‘),(3,‘王五‘,‘ww‘,20,‘15010898065‘,‘[email protected]‘);

/*!40101 SET [email protected]_SQL_MODE */;
/*!40014 SET [email protected]_FOREIGN_KEY_CHECKS */;
/*!40014 SET [email protected]_UNIQUE_CHECKS */;
/*!40111 SET [email protected]_SQL_NOTES */;

if标签

User实体

UserMapper

UserMapper.xml

UserController

测试

http://localhost:8080/getUser

where标签

<select id="getUser" resultType="cn.cnki.ref.pojo.User">
        select * from user
        <where>
            <if test="id != null">and id=#{id} </if>
            <if test="age != null">and age=#{age} </if>
            <if test="name != null">and name=#{name}</if>
        </where>
    </select>

trim标签下的四个属性：

prefix：在标签开始添加上该字符串

suffixOverrides：在标签末尾去除上该字符串

suffix：在标签末尾添加上该字符串

prefixOverrides：在标签开始去除上该字符串

set标签

trim标签

switch\when标签

foreach标签

原文地址：https://www.cnblogs.com/cnki/p/9346333.html