关于mybatis中的resultType与resultMap用法及误区

1.resultType与resultMap

resultType：指定返回数据的类型 如果为List 此处应填对应的java Object 注：select的条件最好与Object里的字段一一对应，避免引发其他错误（大小写敏感）

resultMap：指定返回的数据为定义好的XXXMap，其中的字段必须一一对应（大小写敏感）

2.foreach传参

传入是单一参数List ——foreach里的collection为list

传入是多个参数，需要用Map传参 ——foreach里的collection为map里的key值

3.batch insert

insert on duplicate key and batch

<insert id="batchInsertOnDuplicateDate" parameterType="com.test.op.interfaces.vo.StatisticsDataForFwyyVO" >
<foreach collection="list" item="dataForFwyyVOs" index="index" open="" close="" separator=";">
insert into tb_statistics (create_time,data_time,
...)
values
(
#{dataForFwyyVOs.createTime,jdbcType=VARCHAR},
#{dataForFwyyVOs.dataTime,jdbcType=DATE},
...        )
on duplicate key update
create_time = #{dataForFwyyVOs.createTime,jdbcType=VARCHAR},
...
</foreach>
/*StatisticsDataFwyy batchInsertOnDuplicateDate*/
</insert>

4.batch update

批量执行多条update语句

<update id="updateBySnIds" parameterType="java.util.Map">
<foreach collection="snIds" item="item" index="index" open="" close="" separator=";">
update sn_card
set is_saled = 1, order_num = #{orderNum,jdbcType=VARCHAR},
...
where id = #{item.snId} and version = #{item.version}
</foreach>
/*SNCard updateBySnIds*/
</update>

执行单条update语句

<update id="deleteByIdsIn">
update service_sku
set is_deleted = 1
<if test="#{0} != null and #{0}.size > 0">
where id in
<foreach item="item" index="index" collection="list" open="(" separator="," close=")">
#{item}
</foreach>
</if>

5.case when

<update id="updateBatch" parameterType="java.util.List" >
update tb_address
<trim prefix="set" suffixOverrides=",">
<trim prefix="businessId =case" suffix="end,">
<foreach collection="list" item="item" index="index">
when id=${item.id} then #{item.businessId}
</foreach>
</trim>
<trim prefix="area = case" suffix="end,">
<foreach collection="list" item="item" index="index">
when id=${item.id} then ${item.area}
</foreach>
</trim>
<trim prefix=" province =case" suffix="end,">
<foreach collection="list" item="item" index="index">
when id=${item.id} then ${item.province}
</foreach>
</trim>
<trim prefix=" city =case" suffix="end,">
<foreach collection="list" item="item" index="index">
when id=${item.id} then ${item.city}
</foreach>
</trim>
<trim prefix=" county =case" suffix="end,">
<foreach collection="list" item="item" index="index">
when id=${item.id} then ${item.county}
</foreach>
</trim>
...
updateTime=now()
</trim>
where id in
<foreach collection="list" open="(" close=")" separator="," item="item" index="index" >
${item.
4000
id}
</foreach>
/*address updateBatch*/
</update>

6.otherwise

组合多个查询条件 不建议使用

<select id="countTotalAmountForFwyy" parameterType="java.util.Map" resultType="java.math.BigDecimal">
select sum(actual_price) from tb_order
where
<choose>
<when test="classifyId != 0">
classify_id = #{classifyId,jdbcType=INTEGER}
</when>
<otherwise>
classify_id in (1,2,4)
</otherwise>
</choose>
<choose>
<when test="startDate != null">
and pay_time >= #{startDate,jdbcType=TIMESTAMP} and pay_time <= #{endDate,jdbcType=TIMESTAMP}
</when>
<otherwise>
and pay_time <= #{endDate}
</otherwise>
</choose>
and actual_price > 0 and be_del=false
/*order countTotalAmountForFwyy*/
</select>