提出需求：

根据班级id查询班级信息(带老师的信息)

项目结构：

创建表和数据：<??http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHA+PHByZSBjbGFzcz0="brush:sql;">CREATE TABLE teacher( t_id INT PRIMARY KEY AUTO_INCREMENT, t_name VARCHAR(20) ); CREATE TABLE class( c_id INT PRIMARY KEY AUTO_INCREMENT, c_name VARCHAR(20), teacher_id INT ); ALTER TABLE class ADD CONSTRAINT fk_teacher_id FOREIGN KEY (teacher_id) REFERENCES teacher(t_id); INSERT INTO teacher(t_name) VALUES('LS1'); INSERT INTO teacher(t_name) VALUES('LS2'); INSERT INTO class(c_name, teacher_id) VALUES('bj_a', 1); INSERT INTO class(c_name, teacher_id) VALUES('bj_b', 2);
Teacher实体类：

package com.atguigu.mybatis.bean;

public class Teacher {

	private int id;
	private String name;

	public Teacher(int id, String name) {
		super();
		this.id = id;
		this.name = name;
	}

	public Teacher() {
		super();
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String toString() {
		return "Teacher [id=" + id + ", name=" + name + "]";
	}

}

package com.atguigu.mybatis.bean;

public class Classes {

	private int id;
	private String name;
	private Teacher teacher;

	public Classes(int id, String name, Teacher teacher) {
		super();
		this.id = id;
		this.name = name;
		this.teacher = teacher;
	}

	public Classes() {
		super();
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Teacher getTeacher() {
		return teacher;
	}

	public void setTeacher(Teacher teacher) {
		this.teacher = teacher;
	}

	@Override
	public String toString() {
		return "Classes [id=" + id + ", name=" + name + ", teacher=" + teacher
				+ "]";
	}

}

	
	
	
	
		SELECT * FROM class c,teacher t WHERE c.teacher_id=t.t_id AND c.c_id=#{id}
	
	
		
		
		
			
			
		
	
	
	
	
		SELECT * FROM class WHERE c_id=#{id}
	
	
	
		SELECT t_id id, t_name name FROM teacher WHERE t_id=#{id}
	
	
	
		
		
		
		
	
	 

package com.atguigu.mybatis.utils;

import java.io.InputStream;

import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MybatisUtils {

	public static SqlSessionFactory getFactory() {
		String resource = "conf.xml";
		InputStream inputStream = MybatisUtils.class.getClassLoader().getResourceAsStream(resource);

		SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(inputStream);

		return factory;
	}
}

package com.atguigu.mybatis.test4;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import com.atguigu.mybatis.bean.Classes;
import com.atguigu.mybatis.utils.MybatisUtils;

/*
 * 测试: 一对一关联表查询
 */
public class Test4 {
	
	public static void main(String[] args) {
		
		SqlSessionFactory factory=MybatisUtils.getFactory();
		SqlSession session=factory.openSession();
		
		String statement="com.atguigu.mybatis.bean.classesMapper.getClass";
		statement="com.atguigu.mybatis.bean.classesMapper.getClass2";
		
		Classes c =session.selectOne(statement, 2);
		System.out.println(c);
		
		session.close();
	}
}