php网站开发职责,重庆公司注册网站,在湖南建设人力资源网站,静态网站怎么建设MyBatis关联查询#xff08;二、一对多查询#xff09; 需求#xff1a;查询所有用户信息及用户关联的账户信息。 分析#xff1a;用户信息和他的账户信息为一对多关系#xff0c;并且查询过程中如果用户没有账户信息#xff0c;此时也要将用户信息查询出来#xff0c…MyBatis关联查询二、一对多查询 需求查询所有用户信息及用户关联的账户信息。 分析用户信息和他的账户信息为一对多关系并且查询过程中如果用户没有账户信息此时也要将用户信息查询出来此时左外连接查询比较合适。 基础项目搭建参考第一个mybatis项目的创建和读取数据库信息 MyBatis关联查询一、一对一查询 在上面项目的基础上先编写user表的pojo文件 public class User implements Serializable {private Integer id;private String username;private Date birthday;private String sex;private String address;//多方private ListAccount accountList;public Integer getId() {return id;}public String getUsername() {return username;}public ListAccount getAccountList() {return accountList;}public void setAccountList(ListAccount accountList) {this.accountList accountList;}public void setId(Integer id) {this.id id;}public void setUsername(String username) {this.username username;}public Date getBirthday() {return birthday;}public void setBirthday(Date 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;}Overridepublic String toString() {return User{ id id , username username \ , birthday birthday , sex sex \ , address address \ };} }编写UserMapper.java代码 public interface UserMapper {User getUserById(Integer id);}在UserMapper.xml中编写下列代码 resultMap idgetUserByIdResult typecn.fpl1116.pojo.Userid columnid propertyid/idresult columnusername propertyusername/result columnaddress propertyaddress/result columnsex propertysex/result columnbirthday propertybirthday/!--一堆多使用collection标签指定数据的封装规则--collection propertyaccountList ofTypecn.fpl1116.pojo.Accountid columnaid propertyid/idresult columnuid propertyuid/resultresult columnmoney propertymoney/result/collection/resultMapselect idgetUserById parameterTypeint resultMapgetUserByIdResultSELECT u.*, a.id aid, a.uid uid, a.money money FROM user u LEFT JOIN account a ON u.ida.uid WHERE u.id#{id}/select编写测试方法 Testpublic void testGetUserById(){UserMapper userMapper sqlSession.getMapper(UserMapper.class);User user userMapper.getUserById(41);System.out.println(user);}运行结果如下