mybatis：updatebyexample与updateByExampleSelective

　　MyBatis，通常逆向工程工具生成接口和xml映射文件用于简单的单表操作。

　　有两个方法： updateByExample 和 updateByExampleSelective ，作用是对数据库进行更新操作。（insert和insertSelective也一球样！）

注意：1，区别在于后者比前者多了动态标签<if test="xxx != null">的判断，有空值，不进行插入操作。

　　　2，updateByExampleSelective可以不按主键更新，条件中可以不包含主键；updateByExample条件中必须包含主键。

updateByExample：

 <update id="updateByExample" parameterType="map" >

    update tb_item

    set id = #{record.id,jdbcType=BIGINT},

      title = #{record.title,jdbcType=VARCHAR},

      sell_point = #{record.sellPoint,jdbcType=VARCHAR},

      price = #{record.price,jdbcType=BIGINT},

      num = #{record.num,jdbcType=INTEGER},

      barcode = #{record.barcode,jdbcType=VARCHAR},

      image = #{record.image,jdbcType=VARCHAR},

      cid = #{record.cid,jdbcType=BIGINT},

      status = #{record.status,jdbcType=TINYINT},

      created = #{record.created,jdbcType=TIMESTAMP},

      updated = #{record.updated,jdbcType=TIMESTAMP}

    <if test="_parameter != null" >

      <include refid="Update_By_Example_Where_Clause" />

    </if>

</update>

updateByExampleSelective：

<update id="updateByExampleSelective" parameterType="map" >

    update tb_item

    <set >

      <if test="record.id != null" >

        id = #{record.id,jdbcType=BIGINT},

      </if>

      <if test="record.title != null" >

        title = #{record.title,jdbcType=VARCHAR},

      </if>

      <if test="record.sellPoint != null" >

        sell_point = #{record.sellPoint,jdbcType=VARCHAR},

      </if>

      <if test="record.price != null" >

        price = #{record.price,jdbcType=BIGINT},

      </if>

      <if test="record.num != null" >

        num = #{record.num,jdbcType=INTEGER},

      </if>

      <if test="record.barcode != null" >

        barcode = #{record.barcode,jdbcType=VARCHAR},

      </if>

      <if test="record.image != null" >

        image = #{record.image,jdbcType=VARCHAR},

      </if>

      <if test="record.cid != null" >

        cid = #{record.cid,jdbcType=BIGINT},

      </if>

      <if test="record.status != null" >

        status = #{record.status,jdbcType=TINYINT},

      </if>

      <if test="record.created != null" >

        created = #{record.created,jdbcType=TIMESTAMP},

      </if>

      <if test="record.updated != null" >

        updated = #{record.updated,jdbcType=TIMESTAMP},

      </if>

    </set>

    <if test="_parameter != null" >

      <include refid="Update_By_Example_Where_Clause" />

    </if>

  </update>

UpdateByExampleSelectivce使用：

　　ProLogExample example = new ProLogExample();
　　example.createCriteria().andNameEqualTo(xiaoming.getName());
　　proLogMapper.updateByExampleSelective(xiaoming, example);

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mybatis：updatebyexample与updateByExampleSelective

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