MyBatis特殊SQL的执行

一、模糊查询

 /**
     * 通过用户名模糊查询用户信息
     * @param mohu
     * @return
     */

    List<User> getUserByLike(@Param("mohu") String mohu);

<!--List<User> getUserByLike(@Param("mohu") String mohu);-->
    <select id="getUserByLike" resultType="com.itheima.mybatis.pojo.User">
        select * from tb_user where username like '%${mohu}%';
    </select>

@Test
    public void testGetUserByLike(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SpecialSQLMapper mapper = sqlSession.getMapper(SpecialSQLMapper.class);
        List<User> list = mapper.getUserByLike("a");
        list.forEach(System.out::println);

二、批量删除

 /**
     * 批量删除
     * @param ids
     */
    void deleteMoreUser(@Param("ids") String ids);```
```xml
<!--void deleteMoreUser(@Param("ids") String ids);;-->
    <delete id="deleteMoreUser">
        delete from tb_user where id in ${ids};
    </delete>

    /**
     * 批量删除
     */
 @Test
    public void testDeleteMoreUser() {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SpecialSQLMapper mapper = sqlSession.getMapper(SpecialSQLMapper.class);
        mapper.deleteMoreUser("9,10");
    }

三、动态设置表名

/**
     *动态设置表名，查询用户信息
     * @param tableName
     * @return
     */
    List<User> getUserList(@Param("tableName") String tableName);

    <!--List<User> getUserList(String tableName);-->
    <select id="getUserList" resultType="User">
        select * from ${tableName};
    </select>

    /**
     * 动态设置表名，查询用户信息
     */
    @Test
    public void testGetUserList() {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SpecialSQLMapper mapper = sqlSession.getMapper(SpecialSQLMapper.class);
        List<User> list = mapper.getUserList("tb_user");
        list.forEach(System.out::println);
    }

四、添加功能获取自增的主键

场景模拟：
t_clazz(clazz_id,clazz_name)
t_student(student_id,student_name,clazz_id)
1、添加班级信息
2、获取新添加的班级的id
3、为班级分配学生，即将某学的班级id修改为新添加的班级的id

/**
 * 添加用户信息
 * @param user
 * @return
 * useGeneratedKeys：设置使用自增的主键
 * keyProperty：因为增删改有统一的返回值是受影响的行数，因此只能将获取的自增的主键放在传输的参 
数user对象的某个属性中
 */
int insertUser(User user);

<!--int insertUser(User user);-->
<insert id="insertUser" useGeneratedKeys="true" keyProperty="id">
 insert into t_user values(null,#{username},#{password},#{age},#{sex})
</insert>

public void testJDBC(){
        try {
            Class.forName("");
            Connection connection = DriverManager.getConnection("","","");
            String sql = "insert into tb_user values()";
            PreparedStatement ps = connection.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);
            ps.executeUpdate();
            ResultSet resultSet = ps.getGeneratedKeys();
            resultSet.next();
            resultSet.getInt(1);
        } catch (Exception e) {
            e.printStackTrace();
        }