ibatis动态语句加and 和不加and

<select id="queryGoodsGroupCodeName" parameterClass="String" resultClass="codeTextBean">
          SELECT L4_GDS_GROUP_CD CODE,L4_GDS_GROUP_DESC NAME FROM DM_GDS_GROUP_INF_TD
          <dynamic prepend="WHERE">
            <isNotEmpty property="value" prepend="AND">
                   (L4_GDS_GROUP_CD LIKE '%$value$%' OR L4_GDS_GROUP_DESC LIKE '%$value$%')
            </isNotEmpty>
        </dynamic>
      </select>

    <select id="queryCategoryCodeName" parameterClass="String" resultClass="codeTextBean">
        select HR_DEPT_CD code, DEPT_NM name from dw_rpt.DM_DEPT_TD
        <dynamic prepend="WHERE">
            <isNotEmpty property="value">
                   (HR_DEPT_CD LIKE '%$value$%' OR DEPT_NM LIKE '%$value$%')
            </isNotEmpty>
        </dynamic>
      </select>

第一条查询语句添加了：prepend="AND"，第二条没添加，发现在isNotEmpty属性中是否添加：prepend="AND"   都能运行。