sql in如何避免过滤掉重复数据？（或者用mybatis）

<select id="queryRegulationItemByItemExpress" resultMap="regulationItemInfo">
SELECT <include refid="columns" /> FROM regulation_item_info
WHERE regulation_id IN
<foreach collection="itemExpress" item="regulationId" open="(" close=")" separator=",">
#{regulationId}
</foreach>
AND is_deleted = 0
</select>
比如我查1，2，4，1只能得到3个结果，如何得到四个结果