多表联合查询resultType的返回值
一般数据按参数类型返回
<select id="queryCarIdList" resultType="long">
select id from t_car_car
</select> <select id="queryDept" resultType="string">
SELECT deptname FROM t_car_run where deptid = #{deptid} GROUP BY deptname
</select>根据某字段查询
返回的类型是实体类，因为查询结果数据均为实体类中字段的数据
<select id="queryNumber" resultType="io.renren.modules.generator.entity.TCarRunEntity">
select number from t_car_car where id = #{carid}
</select>查询结果为多条记录，存放在list中返回
返回的类型是实体类，因为查询结果数据均为实体类中字段的数据
<select id="queryCar" resultType="io.renren.modules.generator.entity.TCarCarEntity">
select * from t_car_car
</select>多表联合查询
t_car_cart_car_drivert_car_cardriver
t_car_cardriver存放的两个字段分别是t_car_car和t_car_driver的主键id
解决方案
1.resultType的返回类型是java.util.Map
返回得到的是List中存放的所有数据
<select id="queryDriver" resultType="java.util.Map">
select driverid from t_car_cardriver where carid = #{id}
</select>2.新建一个实体类
里面存放的是查询结果里需要的字段名
// TCarCarDriver
private Long carid;
private Long driverid;返回类型为该实体类
<select id="queryDriver" resultType="TCarCarDriver">
select driverid from t_car_cardriver where carid = #{id}
</select>多表联查,返回结果嵌套list
多层集合嵌套返回结果用resultMap,collection中再次使用resultMap
<resultMap id="chainVo" type="com.suncnpap.intelligentqa.vo.ChainVo">
<id column="cid" property="id"/>
<result column="access_key" property="accessKey"/>
<result column="secret_key" property="secretKey"/>
<result column="outer_chain_name" property="outerChainName"/>
<result column="outer_chain_document" property="outerChainDocument"/>
<collection property="intentionVos" ofType="com.suncnpap.intelligentqa.vo.ChainIntentionVo"
resultMap="intentionVos"/>
</resultMap>
<resultMap id="intentionVos" type="com.suncnpap.intelligentqa.vo.ChainIntentionVo">
<id column="iid" property="id"/>
<result column="intention_name" property="intentionName"/>
<collection property="questionVoList" ofType="com.suncnpap.intelligentqa.vo.MultiQuestionVo">
<id column="qid" property="id"/>
<result column="question" property="question"/>
</collection>
<collection property="wordVos" ofType="com.suncnpap.intelligentqa.vo.ChainIntentionWordVo">
<id column="wid" property="id"/>
<result column="word_slot" property="wordSlot"/>
<result column="word_slot_miss_question" property="wordSlotMissQuestion"/>
<result column="entity_type_ids" property="entityTypeIds"/>
</collection>
</resultMap>
<select id="detail" resultMap="chainVo">
select tc.id as tid,
tci.id as iid,
tciw.id as wid,
tmq.id as qid,
access_key,
secret_key,
outer_chain_name,
outer_chain_document,
intention_name,
question,
word_slot,
word_slot_miss_question,
entity_type_ids
from t_chain tc
left join t_chain_intention tci on tc.id = tci.chain_id
left join t_chain_intention_word tciw on tci.id = tciw.intention_id
left join t_multi_question tmq on tci.id = tmq.parent_id
where tc.id = #{id}
and tc.deleted = 0
</select>以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
