如何在Mybatis中實現(xiàn)一個連接查詢與嵌套查詢功能

#表一：地址國家表
CREATE TABLE address(aid INT AUTO_INCREMENT PRIMARY KEY,aname VARCHAR(20));

INSERT INTO address VALUES(NULL,"魏國");
INSERT INTO address VALUES(NULL,"蜀國");
INSERT INTO address VALUES(NULL,"吳國");


#表二：出場人物表
CREATE TABLE person(
	pid INT AUTO_INCREMENT PRIMARY KEY,
	pname VARCHAR(20),
	paid INT,
	CONSTRAINT pafk FOREIGN KEY person(paid) REFERENCES address(aid) ON UPDATE CASCADE ON DELETE CASCADE
	);
	
INSERT INTO person VALUES(1,"曹操",1);
INSERT INTO person VALUES(2,"荀彧",1);
INSERT INTO person VALUES(3,"張遼",1);

INSERT INTO person VALUES(4,"劉備",2);
INSERT INTO person VALUES(5,"關(guān)羽",2);
INSERT INTO person VALUES(6,"張飛",2);
INSERT INTO person VALUES(7,"諸葛亮",2);

INSERT INTO person VALUES(8,"孫權(quán)",3);
INSERT INTO person VALUES(9,"周瑜",3);
INSERT INTO person VALUES(10,"陸遜",3);

INSERT INTO person VALUES(11,"公孫瓚",NULL);


#表三：交通工具表
CREATE TABLE tool(tid INT AUTO_INCREMENT PRIMARY KEY,tname VARCHAR(20));
INSERT INTO tool VALUES(1,"馬");
INSERT INTO tool VALUES(2,"船");


#表四：地址國家——交通工具 多對多關(guān)系表
CREATE TABLE aandt(
	a_aid INT,
	a_tid INT,
	PRIMARY KEY(a_aid,a_tid),#聯(lián)合主鍵，是指多個字段組成一個組合，該組合在數(shù)據(jù)表中唯一
	CONSTRAINT FOREIGN KEY aandt(a_aid) REFERENCES address(aid) ON UPDATE CASCADE ON DELETE CASCADE,
	CONSTRAINT FOREIGN KEY aandt(a_tid) REFERENCES tool(tid) ON UPDATE CASCADE ON DELETE CASCADE
);

INSERT INTO aandt VALUES(1,1);
INSERT INTO aandt VALUES(2,1);
INSERT INTO aandt VALUES(2,2);
INSERT INTO aandt VALUES(3,2);

<!--多對一的數(shù)據(jù)庫-->
 <mapper namespace="com.fh.dao.PersonDao">
 	<!--該映射的id為map1，該映射的內(nèi)容為：將查詢到的字段的結(jié)果值，按照本映射的對應(yīng)關(guān)系，分別封裝在Person實體類下的各個屬性上，整體構(gòu)成Person-->
 <resultMap id="map1" type="com.fh.domain.Person">
  <id column="pid" property="pid"/><!--id：主鍵映射； column：數(shù)據(jù)庫表字段； property：類中對應(yīng)屬性名-->
  <result column="pname" property="pname"/><!--result：非主鍵映射-->
  <result column="paid" property="paid"/>
  <association property="address" javaType="com.fh.domain.Address"><!--association：在查詢到多，然后對應(yīng)出一時，用于關(guān)聯(lián)對應(yīng)出一的一方； property：查詢類中包含的子對象屬性; javaType：子對象屬性封裝對應(yīng)的類-->
   <id column="aid" property="aid"/>
   <result column="aname" property="aname"/>
  </association>
 </resultMap>
 <select id="findAllPerson" resultMap="map1">/*resultMap:自己編寫的結(jié)果集，本查詢的返回值正是該結(jié)果集所對應(yīng)的映射組構(gòu)成的Person*/
--   查詢所有人及其對應(yīng)的地址，以人為主，則對人側(cè)外連接
  SELECT * FROM person p LEFT OUTER JOIN address a ON p.paid = a.aid
 </select>
</mapper>

<!--一對多的數(shù)據(jù)庫-->
 <mapper namespace="com.fh.dao.AddressDao">
 <resultMap id="map2" type="com.fh.domain.Address">
  <id column="aid" property="aid"/>
  <result column="aname" property="aname"/>
  <collection property="personList" ofType="com.fh.domain.Person"><!--collection：查詢到一，接著關(guān)聯(lián)對應(yīng)出多時，指向多的一方； foType：集合中每個元素所屬的映射類-->
   <id column="pid" property="pid"/>
   <result column="pname" property="pname"/>
   <result column="paid" property="paid"/>
  </collection>
 </resultMap>
 <select id="findAllAddress" resultMap="map2">
  SELECT * FROM address a LEFT OUTER JOIN person p ON a.aid = p.paid;
 </select>
</mapper>

<mapper namespace="com.fh.dao.ToolDao">
 <resultMap id="map3" type="com.fh.domain.Tool">
  <id column="tid" property="tid"/>
  <result column="tname" property="tname"/>
  <collection property="addressList" ofType="com.fh.domain.Address">
   <id column="aid" property="aid"/>
   <result column="aname" property="aname"/>
  </collection>
 </resultMap>
 <select id="findAllTool" resultMap="map3">
  SELECT t.*,a.* FROM tool AS t LEFT OUTER JOIN aandt AS a_t ON t.`tid` = a_t.`a_tid` LEFT OUTER JOIN address AS a ON a_t.`a_aid` = a.`aid`;
 </select>

//查詢所有人，以及其對應(yīng)的地址
 List<Person> findPersonFromAddress();

<!--多對一的數(shù)據(jù)庫-->
 <mapper namespace="com.fh.dao.PersonDao">
 <!--person映射的基本屬性對應(yīng)下面person的結(jié)果集，本結(jié)果集內(nèi)部再繼續(xù)進行處理-->
 <resultMap id="map1" type="com.fh.domain.Person">
  <id column="pid" property="pid"/>
  <result column="pname" property="pname"/>
  <result column="paid" property="paid"/>
  <!--
  對應(yīng)到person內(nèi)的子屬性對象，column內(nèi)為person對應(yīng)到address的外鍵，由此外鍵，傳入select內(nèi)的方法進行二次嵌套查詢，交由AddressDao在其中的指定方法進行處理
  即要求查詢目標(biāo)為：Address.aid = Person.paid
  -->
  <association property="address" column="paid" select="com.fh.dao.AddressDao.findAddressById"/>
 </resultMap>
 <!--第一次查詢?yōu)橹徊樵冎饕獙ο?，自定義結(jié)果集-->
 <select id="findPersonFromAddress" resultMap="map1">
  select * from person
 </select>
</mapper>

//按照id查詢Address
List<Address> findAddressById(Integer id);

 <mapper namespace="com.fh.dao.AddressDao">
 <!--根據(jù)id對address查詢-->
 <select id="findAddressById" resultType="com.fh.domain.Address">
  SELECT * FROM address WHERE aid = #{aid}
 </select>

List<Address> findAddressWithPerson();

<resultMap id="map2" type="com.fh.domain.Address">
  <id column="aid" property="aid"/>
  <result column="aname" property="aname"/>
  <collection property="personList" column="aid" select="com.fh.dao.PersonDao.findPersonById"/>
 </resultMap>
 <select id="findAddressWithPerson" resultMap="map2">
  select * from address
 </select>

 List<Person> findPersonById(Integer id);

<select id="findPersonById" resultType="com.fh.domain.Person">
  select * from person where pid = #{pid}
 </select>

<settings>
  <setting name="lazyLoadingEnable" value="true"/>
  <setting name="lazyLoadTriggerMethods" value="true"/><!--本條設(shè)置表示將包括原本不會延遲加載的equals/clone/hashCode/toString在內(nèi)所有方法進行延遲加載-->
 </settings>