MyBatis one-to-one correlation table query

Create a table first

CREATE TABLETeacher (t_idINT PRIMARY KEYAuto_increment,t_nameVARCHAR( -));CREATE TABLEClass (c_idINT PRIMARY KEYAuto_increment,c_nameVARCHAR( -), teacher_idINT);ALTER TABLEClassADD CONSTRAINTfk_teacher_idFOREIGN KEY(teacher_id)REFERENCESteacher (t_id);INSERT  intoTeacher (T_name)VALUES('LS1');INSERT  intoTeacher (T_name)VALUES('LS2');INSERT  intoClass (C_name, teacher_id)VALUES('bj_a',1);INSERT  intoClass (C_name, teacher_id)VALUES('Bj_b',2);

To define an entity class:

 Public class Teacher {privateint  ID; Private String name;}

 Public class Classes {    privateint  ID;     Private String name;     Private Teacher Teacher;}

There are two ways to query for what you want to see in two tables:

 select  *   class C, teacher T where  c.teacher_id =  t.t_id and  c.c_id=  #{id}//Union Table query /pre>

SELECT *  from WHERE c_id=1; SELECT *  from WHERE t_id=1//1 is the value of the teacher_id from the previous query              //multi-table query

mapping files for the first way:

<SelectID= "GetClass"ParameterType= "int"Resultmap= "Getclassmap">SELECT * from class C, teacher T where c.teacher_id=t.t_id and C.c_id=#{id}</Select>    <Resultmaptype= "Classes"ID= "Getclassmap">        <ID Property= "id"column= "c_id"/>        <result Property= "Name"column= "C_name"/>        <Association Property= "Teacher"Javatype= "Teacher">            <ID Property= "id"column= "t_id"/>            <result Property= "Name"column= "T_name"/>        </Association>    </Resultmap>

Mapping file for the second way

<SelectID= "GetClass2"Resultmap= "Getclass2map">SELECT * from class where C_id=#{id}</Select>    <SelectID= "Getteacher"Resulttype= "Teacher">Select t_id ID, t_name name from teacher where T_id=#{id}</Select>    <Resultmaptype= "Classes"ID= "Getclass2map">        <ID Property= "id"column= "c_id"/>        <result Property= "Name"column= "C_name"/>        <Association Property= "Teacher"column= "teacher_id"Select= "Getteacher">        </Association>    </Resultmap>

MyBatis one-to-one correlation table query