mybatis 多表关联mapper文件写法操作

两张表SystemParam（系统参数表） Suit （主题）

SystemParam 与 Suit 是多对一

Suit 的higerSuit字段是Suit 的父及主题id 是多对一，需要自连接查询，因为重名所以父表sql字段加别名

mapper方法

Systemparam selectJoinSuit(String strparamcode);

Po类

public class Systemparam { //ManyToOne '主题' private Suit suitobj; private String strparamcode; private String strenable; private String strparamname; //suit表主键 private String suit; private String strparamvalue;｝ public class Suit { //ManyToOne private Suit suit; //主键 private String strsuitcode; private String strsuitname; //父级id private String higersuit;｝

resultMap的写法

<resultMap type='net.transino.model.Systemparam' > <id column='strParamCode' property='strparamcode' jdbcType='VARCHAR' /> <result column='strEnable' property='strenable' jdbcType='VARCHAR' /> <result column='strParamName' property='strparamname' jdbcType='VARCHAR' /> <result column='suit' property='suit' jdbcType='VARCHAR' /></resultMap>

resultMap 使用extends 继承上级map

<resultMap type='net.transino.model.Systemparam' extends='BaseResultMap' > <result column='strParamValue' property='strparamvalue' jdbcType='LONGVARCHAR' /></resultMap><resultMap type='net.transino.model.Systemparam' extends='ResultMapWithBLOBs' > <association property='suitobj' javaType='Suit'> <id column='strSuitCode' property='strsuitcode' jdbcType='VARCHAR' /> <result column='strSuitName' property='strsuitname' jdbcType='VARCHAR' /> <result column='higerSuit' property='higersuit' jdbcType='VARCHAR' /> <association property='suit' javaType='Suit'> <id column='pstrSuitCode' property='strsuitcode' jdbcType='VARCHAR' /> <result column='pstrSuitName' property='strsuitname' jdbcType='VARCHAR' /> <result column='phigerSuit' property='higersuit' jdbcType='VARCHAR' /> </association> </association></resultMap>

select写法

<select resultMap='JoinsuitMap' parameterType='java.lang.String'> select systempara0_.*, suit1_.*, suit2_.strSuitCode pstrSuitCode, suit2_.strSuitName pstrSuitName, suit2_.higerSuit phigerSuit from SystemParam systempara0_ LEFT OUTER JOIN Suit suit1_ ON systempara0_.suit=suit1_.strSuitCode LEFT OUTER JOIN Suit suit2_ ON suit1_.higerSuit=suit2_.strSuitCode WHERE systempara0_.strParamCode=#{strparamcode,jdbcType=VARCHAR}</select>

补充知识：Mybatis中resultMap标签实现多表查询（多个对象）

1 n+1

1 在teacher中添加List student，

public class Teacher { private int id; private String name; private List<Student> list;

2 在studentMapper.xml中添加通过tid查询

<select resultType='Student' parameterType='int'> select * from student where tid=#{0}</select>

3 在TeacherMapper.xml中添加查询全部

<resultMap type='Teacher' id='mymap1'> <id column='id' property='id'/> <result column='name' property='name'/> <collection property='list' ofType='Student' select='com.bjsxt.mapper.StudentMapper.selByTid' column='id'></collection></resultMap> <select resultMap='mymap1'> select * from teacher </select>

其中collection是当属性为集合类型时使用的标签

2 多表联合

<resultMap type='Teacher' id='stumap1'> <id column='tid' property='id'/> <result column='tname' property='name'/> <collection property='list' ofType='Student'> <id column='sid' property='id'/> <result column='sname' property='name'/> <result column='age' property='age'/> <result column='tid' property='tid'/> <association property='teacher' select='com.bjsxt.mapper.TeacherMapper.selById' column='tid'></association> </collection> </resultMap> <select resultMap='stumap1'> select t.id tid,t.name tname,s.id sid,s.name sname,age,tid from teacher t left join student s on t.id=s.tid </select>

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