1.Mybatis多表查询

1.1一对一查询

        1.一对一查询的模型

public class Order {         private int id;         private Date ordertime;         private double total;         //代表当前订单从属于哪一个客户         private User user; }

 

public class User {         private int id;         private String username;         private String password;         private Date birthday; }

        3.创建OrderMapp接口

 

public interface OrderMapper {         List findAll(); }

        4.配置OrderMapper.xml

SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id

 1.2 一对多查询

        1.一对多查询的模型

public class Order {         private int id;         private Date ordertime;         private double total;         //代表当前订单从属于哪一个客户         private User user; }

public class User {         private int id;         private String username;         private String password;         private Date birthday;         //代表当前用户具备哪些订单         private List orderList; }

         4.创建UserMapper接口

public interface UserMapper {         List findAll(); }

        5.配置UserMapper.xml

SELECT*,o.id oid FROM orders o,USER u WHERE u.id=o.uid

 1.3 多对多查询

        1.多对多查询的模型

public class User {         private int id;         private String username;         private String password;         private Date birthday;          //代表当前用户具备哪些订单         private List orderList;         //代表当前用户具备哪些角色         private List roleList; }

 

public class Role {         private int id;         private String rolename; }

        3.添加UserMapper接口方法

 List findAllUserAndRole();

        5.配置UserMapper.xml

SELECT*FROM user u,sys_user_role ur,sys_role r WHERE u.id=ur.userid AND ur.roleid=r.id