mybatis的selectKey作用详解

<selectKey resultType="java.lang.Integer" order="AFTER" keyProperty="id">
SELECT LAST_INSERT_ID() AS ID 
</selectKey> 

<insert id="insert" parameterType="com.pinyougou.pojo.TbGoods" >
    <selectKey resultType="java.lang.Long" order="AFTER" keyProperty="id">
      SELECT LAST_INSERT_ID() AS id
    </selectKey>
    insert into tb_goods (id, seller_id, goods_name,
      default_item_id, audit_status, is_marketable, 
      brand_id, caption, category1_id, 
      category2_id, category3_id, small_pic, 
      price, type_template_id, is_enable_spec, 
      is_delete)
    values (#{id,jdbcType=BIGINT}, #{sellerId,jdbcType=VARCHAR}, #{goodsName,jdbcType=VARCHAR}, 
      #{defaultItemId,jdbcType=BIGINT}, #{auditStatus,jdbcType=VARCHAR}, #{isMarketable,jdbcType=VARCHAR}, 
      #{brandId,jdbcType=BIGINT}, #{caption,jdbcType=VARCHAR}, #{category1Id,jdbcType=BIGINT}, 
      #{category2Id,jdbcType=BIGINT}, #{category3Id,jdbcType=BIGINT}, #{smallPic,jdbcType=VARCHAR}, 
      #{price,jdbcType=DECIMAL}, #{typeTemplateId,jdbcType=BIGINT}, #{isEnableSpec,jdbcType=VARCHAR}, 
      #{isDelete,jdbcType=VARCHAR})
  </insert>

<insert id="insertCheckGroup"  parameterType="com.zyl.pojo.CheckGroup">
        <selectKey resultType="int" keyProperty="id" order="AFTER">
            SELECT LAST_INSERT_ID()
        </selectKey>
        insert into check_group (name) value (#{name});
</insert>

int insertCheckGroup(CheckGroup checkGroup);

int insertCheckGroup(@Param("test") CheckGroup checkGroup);

<insert id="insertCheckGroup"  parameterType="com.zyl.pojo.CheckGroup">
        <selectKey resultType="int" keyProperty="test.id" order="AFTER">
            SELECT LAST_INSERT_ID()
        </selectKey>
        insert into check_group (name) value (#{name});
</insert>