Mybatis一对一关系映射

示例:学生--班级--房间

查询学生的同时，查询班级名，房间地址

方式一：嵌套查询

    
        
        
        
        association标签，将班级信息映射到StudentBean对象中的classBean属性中 
        
            
        
        
        
            
        
    

    
            SELECT s.*,r.r_address,c.c_name
            FROM t_student s ,t_room r ,t_class c
            WHERE s.fk_roomid=r.pk_roomid AND s.fk_classid = c.pk_classid
    

方式二：联表查询

    
    
    

    
    

    
    



    SELECT s.*, c.*, r.*
    FROM t_student s 
    JOIN t_class c ON s.fk_classid = c.pk_classid
    JOIN t_room r ON s.fk_roomid = r.pk_roomid

    
    
    



    
    



    
    



    SELECT s.*, c.*, r.*
    FROM t_student s 
    JOIN t_class c ON s.fk_classid = c.pk_classid
    JOIN t_room r ON s.fk_roomid = r.pk_roomid