MyBatis--动态SQL（set的用法）

 　　先修改UserMapper.xml中的selectById方法,代码如下：

<update id="updateById">
        update sys_user
        <set>
        <if test="userName != null and userName !=''">
            user_name =#{userName},
        </if>
        <if test="userPassword != null and userPassword != ''">
            user_password =#{userPassword},
        </if>
        <if test="userEmail != null and userEmail != ''">
            user_email =#{userEmail},
        </if>
        <if test="userInfo != null and userInfo != ''">
            user_info =#{userInfo},
        </if>
        <if test="headImg != null">
            head_img =#{headImg},
        </if>
        <if test="createTime != null">
            create_time =#{createTime},
        </if>
            id =#{id}
        </set>
        where id =#{id}
    </update>

注意和在update更新列中使用if标签的区别！！！