1：查询过滤条件不为空：
<select id="getActivityByIdAndEx" resultMap="BaseResultMap" >
select
<include refid="Base_Column_List"/>
from
experiencesend where userId=#{userId} and experienceId=#{experienceId} and changeCode is not null
</select>
2：动态sql小技巧：
<select id="selectEntity" resultMap="BaseResultMap" parameterType="com.yhb.jsxn.entity.ActivityUserApply" >
select
<include refid="Base_Column_List" />
from activity_user_apply
<where>
<if test="userPhone != null">
User_Phone = #{userPhone}
</if>
</where>
<if test="pageSize != null and pageSize != 0">
<if test="pageNo != null and pageSize != null">
limit #{pageNo},#{pageSize}
</if>
</if>
</select>