mybatis mapper

mybatis

    
    
    
    
    



    SELECT * FROM USER WHERE id=#{id}


    INSERT INTO USER (username,birthday,sex,address)VALUES (#{username},#{birthday},#{sex},#{address})


    SELECT * FROM USER



    UPDATE  USER SET username=#{username} WHERE id=#{id}




    
        SELECT LAST_INSERT_ID()
    
    INSERT  INTO USER (username,birthday,sex,address)
    VALUES (#{username},#{birthday},#{sex},#{address})



    SELECT username,COUNT(*) as count FROM USER GROUP BY username ORDER BY count DESC

mapper

    
        
        
        
        
        
    

    
        SELECT * FROM USER WHERE id=#{id}
    

• namespace 命名空间是对应的mapper的全限定名称。

resultMap bean属性与数据库字段对应关系

• 当Java bean 属性与数据库字段不一致时，需要一个对应关系，resultMap表示对应关系。
• id（唯一） 用于select标签 的resultMap属性值。
• type java bean 全限定名称。
• property bean的属性名称。
• column 数据库字段名称。

普通sql

select

    SELECT * FROM USER WHERE id=#{id}
 

• id 对应mapper 的方法。
• parameterType 输入参数类型。
• resultType最小对象粒度 这里返回的数据是List
  对应的resultType 是User。
• "#{id}" 表示占位符。

update

    UPDATE  USER SET username=#{username} WHERE id=#{id}

返回插入的id

  
    
        SELECT LAST_INSERT_ID()
    
    INSERT  INTO USER (username,birthday,sex,address)
    VALUES (#{username},#{birthday},#{sex},#{address})

聚合操作

    SELECT username,COUNT(*) as count FROM USER GROUP BY username ORDER BY count DESC

• resultType 这里返回的数据类型是List>
  所以resultYpe对应的最小粒度是map。

分页

    SELECT * FROM USER limit #{start},#{count}


@RequestMapping("fenye")
public String fenye(Model model, Integer start) {
    Map parameter = new HashMap<>();
    parameter.put("start",start*5);
    parameter.put("count",5);
    List datas = userService.fenye(parameter);
    System.out.println(datas);
    model.addAttribute("name", datas);
    return "demo";
}

动态sql操作

动态查询

    

    SELECT * FROM USER
    
        
            AND username LIKE #{pname}
        
        
            AND address=#{paddress}
        

    

动态更新

    update USER
      
          
              username=#{username},
          
          
              address=#{address},
          
      
     WHERE id=#{id}

• 不用写set 最后“,” 自动删除。

动态删除

    delete from user where id in
    
        ${ids}
    

动态插入

    
        
            id,
        
        
            username,
        
        
            birthday,
        
        
            address,
        
        
            sex,
        
    




    
        
            #{id},
        
        
            #{username},
        
        
            #{birthday},
        
        
            #{address},
        
        
            #{sex},
        
    



    insert into USER() VALUES ()

联表查询

bean

public class User implements Serializable {

    private Integer id;
    private String username="";
    private String birthday;
    private String sex;
    private String address;

    private List
 addressList = new ArrayList<>();

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getBirthday() {
        return birthday;
    }

    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public List
 getAddressList() {
        return addressList;
    }

    public void setAddressList(List
 addressList) {
        this.addressList = addressList;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday='" + birthday + '\'' +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                ", addressList=" + addressList +
                '}';
    }
}

---

public class Address {
    private int id;
    private String name;
    private User user;

    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 User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }


    @Override
    public String toString() {
        return "Address{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}    

一对一 一个地址对应一个用户

AddressMapper.xml

    
        
        
    

    
        
        
        
    


    
        SELECT a.name,u.username FROM address a INNER JOIN user u ON a.uid=u.id  AND a.id=#{id}
    

• association 联合查询 相当于引入。
• property 属性 type 指向的bean的属性名称。
• resultMap 由namespace+resultMap的id组成。
• 这里的select resultMap选择是address2.

一对多 一个用户对应多个地址

    
        
        
        
        
        
        
    

    
         SELECT u.username,a.* FROM user u INNER JOIN  address a ON a.uid=u.id AND u.id=#{id}