MyBatis动态SQL使用，传入参数Map中的Key判断

<select id="" parameterType="Map" resultMap="commodityResultMap" >
SELECT c.id c_id,c.variety_id,c.nickName c_nickName,c.description c_description,c.ordinaryPrice c_ordinaryPrice,c.memberPrice c_memberPrice,c.path c_path,v.id v_id,v.nickName v_nickName
FROM commodity c
INNER JOIN variety v
ON c.variety_id=v.id
where 1=1 <!-- _parameter.containsKey('键') 作用：判断键是否存在返回值boolean #{键}取对应的值 ！必须三处键值对应，否则取不到值-->
<if test="_parameter.containsKey('varietyID')">
and v.id=#{varietyID}
</if>
</select>

• 此做法的好处，可做多条件查询。