Eins: Verwenden Sie dynamisches SQL, um eine Abfrage mit mehreren Bedingungen abzuschließen
a: Verwenden Sie if+where, um eine Abfrage mit mehreren Bedingungen zu implementieren
Zunächst einmal die Szenarioanforderungen, es gibt eine Note und Klassentabelle, die erste Anforderung ist eine bedingte Abfrage basierend auf dem Namen und dem Alter der Fuzzy-Abfrage, Schnittstellenschichtmethode
public List<student> getStudentByIf(student stu);
Als nächstes folgt die Konfiguration der Zuordnungsdatei
<select id="getStudentByIf" parameterType="stu" resultType="stu">select * from student <where> <if test="stuAge!=0"> and stuAge>#{stuAge} </if> <if test="stuName!=null"> and stuName LIKE '%' #{stuName} '%' </if> </where></select>
Test
studentDao dao = MyBatis.getSessionTwo().getMapper(studentDao.= "z"List<student> list="----------"+
---- ------zhangyu<br/>----------zy<br/>----------zy<br/>----------zhang
<br/>
b: Wählen Sie bei der Klassifizierung
Diese Methode entspricht dem Prinzip der Auswahl der Schleifenstruktur in Java. Um mehrere Situationen zu beurteilen, ändern Sie einfach die Mapping-Datei
Schnittstellenklasse
public List<student> getAllStudentByLike(Map<String, Object> userMap); //使用map作为参数
Mapping-Datei
<span style="color: #0000ff"><</span><span style="color: #800000">select </span><span style="color: #ff0000">id</span><span style="color: #0000ff">="getAllStudentByLike"</span><span style="color: #ff0000"> parameterType</span><span style="color: #0000ff">="Map"</span><span style="color: #ff0000"> resultType</span><span style="color: #0000ff">="stu"</span><span style="color: #0000ff">></span><span style="color: #000000">select * from student</span><span style="color: #0000ff"><</span><span style="color: #800000">where</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">choose</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">when </span><span style="color: #ff0000">test</span><span style="color: #0000ff">="stuName!=null"</span><span style="color: #0000ff">></span><span style="color: #000000"> stuName like CONCAT('%',#{stuName},'%')</span><span style="color: #0000ff"></</span><span style="color: #800000">when</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">when </span><span style="color: #ff0000">test</span><span style="color: #0000ff">="stuAge!=0"</span><span style="color: #0000ff">></span><span style="color: #000000"> stuAge> #{stuAge}</span><span style="color: #0000ff"></</span><span style="color: #800000">when</span><span style="color: #0000ff">><br/></span><otherwise>
1=1
</otherwise><span style="color: #0000ff"><br/></span><span style="color: #0000ff"></</span><span style="color: #800000">choose</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">where</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">select</span><span style="color: #0000ff">></span>
Ergebnis
zhangyu zy zy zhang
c: Es gibt drei Möglichkeiten um foreach zum Abschließen komplexer Abfragen zu verwenden,
Der erste Typ: Der eingehende Parameter ist ein Array-Typ
🎜>
//传一组 xueshengID public List<student> getStudentBystuId_foreach_array(Integer[] ints);
映射文件配置 <!--跟据学生id查询学生Interger-->
<select id="getStudentBystuId_foreach_array" resultMap="studentList">select * from student<if test="array.length>0">where stuId IN/*数组形式传入学生Id*/<foreach collection="array" item="stu" open="(" separator="," close=")"> #{stu}</foreach>
</if>
</select>
Der zweite Typ: Übergabe der Listensammlung
Integer[] ints = {2,3,4};
List<student> list = dao.getStudentBystuId_foreach_array(ints);for (student item:list) {
System.out.println(item.getStuName());
}
public List<student> getStudentBystuId_foreach_list(List<Integer> list);
Test:
<!--跟据学生id查询学生list方式--><select id="getStudentBystuId_foreach_list" resultMap="studentList">select * from student<if test="list.size>0">where stuId IN
/*集合形式传入学生Id*/<foreach collection="list" item="stu" open="(" separator="," close=")">#{stu}</foreach></if></select>
Der dritte Typ: Nach Karte einstellen
>
studentDao dao = MyBatis.getSessionTwo().getMapper(studentDao.class);
Integer ints = 2;
List<Integer> list = new ArrayList<Integer>();
list.add(ints);
List<student> stulist = dao.getStudentBystuId_foreach_list(list);
for (student item:stulist) {
System.out.println(item.getStuName());
}
public List<student> getStudentBystuId_foreach_map(Map<String, Object> stuMap);
<!--跟据学生id查询学生map方式--><select id="getStudentBystuId_foreach_map" resultMap="studentList">select * from student where stuId IN
/*集合形式传入学生Id*/<foreach collection="stuId" item="stu" open="(" separator="," close=")"> <!--collection是自己定义的，就是map的key值-->#{stu}</foreach></select>
<span style="color: #008000"> Map<String ,Object> stumap = new HashMap<String, Object>();
List<Integer> listStuId = new ArrayList<Integer>();
listStuId.add(2);
listStuId.add(3);
listStuId.add(4);
stumap.put("stuId",listStuId);
List<student> list = dao.getStudentBystuId_foreach_map(stumap);
for (student item:list
) {
System.out.println(item.getStuName());
}</span><span style="color: #008000"><br/></span>
public grade getGradeById(int gradeId);
<span style="color: #008000"><!--</span><span style="color: #008000">实现一 对多的第一中实现</span><span style="color: #008000">--></span><span style="color: #0000ff"><</span><span style="color: #800000">resultMap </span><span style="color: #ff0000">id</span><span style="color: #0000ff">="gradeMapOne"</span><span style="color: #ff0000"> type</span><span style="color: #0000ff">="grade"</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">id </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeId"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeId"</span><span style="color: #0000ff">></</span><span style="color: #800000">id</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeName"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeName"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">collection </span><span style="color: #ff0000">property</span><span style="color: #0000ff">="gatStudent"</span><span style="color: #ff0000"> ofType</span><span style="color: #0000ff">="stu"</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">id </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="stuUd"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="stuId"</span><span style="color: #0000ff">></</span><span style="color: #800000">id</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="stuName"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="stuName"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="stuAge"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="stuAge"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">collection</span><span style="color: #0000ff">></span><span style="color: #0000ff"></</span><span style="color: #800000">resultMap</span><span style="color: #0000ff">></span><span style="color: #008000"><!--</span><span style="color: #008000">实现一 对多的第二中实现</span><span style="color: #008000">--></span><span style="color: #0000ff"><</span><span style="color: #800000">resultMap </span><span style="color: #ff0000">id</span><span style="color: #0000ff">="gradeMap"</span><span style="color: #ff0000"> type</span><span style="color: #0000ff">="entity.grade"</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">id </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeId"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeId"</span><span style="color: #0000ff">></</span><span style="color: #800000">id</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">result </span><span style="color: #ff0000">column</span><span style="color: #0000ff">="gradeName"</span><span style="color: #ff0000"> property</span><span style="color: #0000ff">="gradeName"</span><span style="color: #0000ff">></</span><span style="color: #800000">result</span><span style="color: #0000ff">></span><span style="color: #0000ff"><</span><span style="color: #800000">collection </span><span style="color: #ff0000">property</span><span style="color: #0000ff">="gatStudent"</span><span style="color: #ff0000"> ofType</span><span style="color: #0000ff">="student"</span><span style="color: #ff0000"> select</span><span style="color: #0000ff">="getStudentById"</span><span style="color: #ff0000"> column</span><span style="color: #0000ff">="gradeId"</span><span style="color: #0000ff">></</span><span style="color: #800000">collection</span><span style="color: #0000ff">> <!--column的值主要作为下次查询的条件，既查询学生的条件--></span><span style="color: #0000ff"></</span><span style="color: #800000">resultMap</span><span style="color: #0000ff">><br/></span>
<select id="getGradeById" resultMap="gradeMapOne">select * from grade,student where grade.gradeId = student.stuGrade and gradeId = #{gradeId}</select><!--ddddddddddddddddddd--><select id="getGradeById" resultMap="gradeMap">select * from grade where gradeId=#{gradeId}</select><select id="getStudentById" resultType="entity.student">select * from student where stuGrade = #{stuGrade}</select><br/>
==> Vorbereiten: Wählen Sie * aus Klasse,Student, wobei grade.gradeId = student.stuGrade und gradeId = ? = ===A sql
==> Parameter: 1(Ganzzahl)<br/>
<== Zeile: 1, S1297, 4, zy, 21, 1
<== Gesamt: 3zhangyu
zyzy
@Testpublic void TestConn(){
gradeDao dao = MyBatis.getSessionTwo().getMapper(gradeDao.class);
grade grade = dao.getGradeById(1); for (student item:grade.getGatStudent() ) {
System.out.println(item.getStuName());
}
}= ===> Parameter: 1(Long)
<==== Spalten: stuId, stuName, stuAge, stuGrade<==== Zeile: 2, zhangyu, 19, 1
<==== using ’ ’ ’ s ’ through 3, zy-- 20, 1<==== = = Gesamt: 1
zhangyu
zy
zy
Prozess beendet mit Exit-Code 0
Das obige ist der detaillierte Inhalt vonErläuterung der Abfrage mit mehreren Bedingungen in MyBatis. Für weitere Informationen folgen Sie bitte anderen verwandten Artikeln auf der PHP chinesischen Website!
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