MyBatis的动态SQL操作--查询

时间:2022-11-07 12:25:12

查询条件不确定,需要根据情况产生SQL语法,这种情况叫动态SQL,即根据不同的情况生成不同的sql语句。

模拟一个场景,在做多条件搜索的时候,

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" alt="" />

对于以上四种情况,sql语句分别是:

1.select * from student
2.select * from student where name='zhangsan'
3.select * from student where sal=1000
4.select * from student where name='zhangsan' and sal = 1000

原来在拼接的时候是这样做的(电力项目的时候就是这样拼接的。。)

select * from student where 1=1 and name='zhangsan'
select * from student where 1=1 and sal=1000
select * from student where 1=1 and name='zhangsan' and sal = 1000

mybatis可以在xml文件中判断

SELECT * FROM student
<where>
  <if test="pid!=null">
    AND id = #{pid}
  </if>
  <if test="pname!=null">
    AND name = #{pname}
  </if>
  <if test="psal!=null">
    AND sal = #{psal}
  </if>
</where>

StudentMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!--
namespace的取值可以是实体的全限定名,这样有好处!
-->
<mapper namespace="com.winner.entity.Student">
<resultMap id="studentMap" type="Student">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="sal" column="sal"/>
</resultMap>
<select id="findAll" parameterType="map" resultMap="studentMap">
SELECT * FROM student
     <!--可以认为<where>标签等价于where 1=1-->
<where>
       <!--pid是map中的key,自动去取map中的value,像后面的#{}中也是map的key,不要写value-->
<if test="pid!=null">
AND id = #{pid}
</if>
<if test="pname!=null">
AND name = #{pname}
</if>
<if test="psal!=null">
AND sal = #{psal}
</if>
</where>
</select>
</mapper>
public class StudentDao {
/**
* 有条件的查询所有学生
*/
public List<Student> findAll(Integer id,String name,Double sal) throws Exception{
SqlSession sqlSession = null;
try{
sqlSession = MybatisUtil.getSqlSession();
       //方法的参数使用map进行接收
Map<String,Object> map = new LinkedHashMap<String,Object>();
map.put("pid",id);
map.put("pname",name);//模糊查询的话加%+name+%
map.put("psal",sal);
return sqlSession.selectList(Student.class.getName()+".findAll",map);
}catch(Exception e){
e.printStackTrace();
throw e;
}finally{
MybatisUtil.closeSqlSession();
}
} public static void main(String[] args) throws Exception { StudentDao dao = new StudentDao();
//查询所有
//List<Student> studentList = dao.findAll(null,null,null);
//List<Student> studentList = dao.findAll(5,null,null);
List<Student> studentList = dao.findAll(null,null,1000d);
for(Student s : studentList){
System.out.println(s.getId()+":"+s.getName()+":"+s.getSal());
}
}
}

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