mybatis(动态sql)

Posted 2021-01-15 xfishs

1.动态sql-if

　　当有值输入才进行sql的动态拼接　　

<!-- 动态sql-if-->
    <select id="selectPersonByName" resultType="Person">
        select * from `person` where `age` > #{age}
        <if test="value != null and value != ‘‘">
            and `name` like ‘%${value}%‘
        </if>
    </select>

/*动态sql-if测试*/
    @Test
    public void selectPersonByName() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
        List<Person> persons = personMapper.selectPersonByName(5,"四");
        sqlSession.close();
        System.out.println(persons);
    }

2.choose-when-otherwise

<!-- 动态sql choose-when-otherwise -->
    <!-- when 当有匹配时候执行拼接，  都没有匹配时，拼接otherwise    （和 switch case 意思相近）-->
    <select id="selectPersonByAgeOrName" parameterType="Person" resultType="Person">
        select * from `person`
        where `id` > 0
        <choose>
            <when test="name != null and name != ‘‘">
                and name like #{name}
            </when>
            <when test="age != null and age != ‘‘">
                and age > #{age}
            </when>
            <otherwise>
                and `age`>`id`
            </otherwise>
        </choose>
    </select>

/*<!-- 动态sql choose-when-otherwise -->*/
    @Test
    public void selectPersonByAgeOrName() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
        Person person = new Person();
        //person.setName("%四%");
        List<Person> persons = personMapper.selectPersonByAgeOrName(person);
        sqlSession.close();
        System.out.println(persons);
    }

3.sql-where  (前面写的where `id` > 0比较无脑， 但是 不写会出现sql语法错误)

<!-- 动态sql where-->
    <!-- 第一个if中 不写and  后面的if中必须写 -->
    <select id="selectPersonByNameOrAge" parameterType="Person" resultType="Person">
        select * from person
        <where>
            <if test="name != null and name != ‘‘">
                `name` like #{name}
            </if>
            <if test="age != null and age != 0">
                and `age` = #{age}
            </if>
        </where>
    </select>

/*<!-- 动态sql where -->*/
    @Test
    public void selectPersonByNameOrAge() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
        Person person = new Person();
        person.setName("%五%");
        person.setAge(11);
        Person persons = personMapper.selectPersonByNameOrAge(person);
        sqlSession.close();
        System.out.println(persons);
    }

4.动态sql-set

<!-- 动态sql set-->
    <!-- 避免先查询再修改，只修改指定列 -->
    <update id="updatePersonByCondition" parameterType="Person">

        UPDATE `person`
        <set>
        <if test="name != null and name != ‘‘">`name` = #{name} ,</if>
        <if test="age != null and age != 0"> `age`=#{age} </if>
        </set>
        WHERE (`id`=#{id})

    </update>

/*<!-- 动态sql set-->*/
    @Test
    public void updatePersonByCondition() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
        Person person = new Person("王炸",50);
        person.setId(3);
        int count = personMapper.updatePersonByCondition(person);
        sqlSession.commit();
        sqlSession.close();
        System.out.println("更新了 count = " + count + "条记录");
    }

5.sql-trim (加前缀，去掉多余的部分  可以替换sql-set 特可以替换 sql-where 使用灵活)

<!-- 动态sql trim-->
    <select id="selectPersonByNameOrAgeTrim" parameterType="Person" resultType="Person">
        select * from person
        <trim prefix="where" suffixOverrides="or | and">
            <!-- 与where作用一样  prefix 加前缀，suffixOverrides 去掉多余的 -->
            <if test="name != null and name != ‘‘">
                `name` like #{name}
            </if>
            <if test="age != null and age != 0">
                and `age` = #{age}
            </if>
        </trim>
    </select>

@Test
    public void selectPersonByNameOrAgeTrim() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
        Person person = new Person();
        person.setName("%h%");
        List<Person> persons = personMapper.selectPersonByNameOrAgeTrim(person);
        sqlSession.close();
        System.out.println(persons);
    }

6.sql-foreach

<!-- 动态sql foreach-->
    <delete id="deletePersonList" parameterType="list">
        delete from `person` where id in
        <foreach collection="list" item="id" open="(" separator="," close=")">
         <!--<foreach collection="传递进来的参数类型 如list arra" item="迭代变量，随意" open="开始符号" separator="分割符号" close="结束符号">
             执行结果 (1,2,3)    -->
            #{id}
        </foreach>
    </delete>

@Test
    public void deletePersonList() {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
        List<Integer> idList = new ArrayList<>();
        idList.add(2);
        idList.add(5);
        int count = personMapper.deletePersonList(idList);
        sqlSession.commit();
        sqlSession.close();
        System.out.println("删除记录 count = " + count);
    }