Mybatis高级功能

应用场景：
应用所取的结果集中需要嵌入别的SQL的结果集。

<resultMap type="com.kevin.wallet.dto.CardsDetailResponse" id="cardsDetailResponse"> 
    	<result property="walletID" column="wallet_id"/>
    	<result property="totalAmount" column="totalAmount"/>
    	<result property="pageNumber" column=""/>
    	<result property="totalNumber" column="totalNumber"/>
    	[color=red]<association property="bailianAmount"  column="{id=WALLET_ID}" select="getBailianAmount" />
    	<association property="okAmount" column="{id=WALLET_ID}" select="okAmount" />[/color]
    	[color=yellow]<collection property="cards" ofType="com.kevin.wallet.dto.ListCardInforResponse" >
    	 <result property="cardNo" column="CARD_ID"/>  
		   <result property="cardName" column="CARD_NAME"/>  
		   <result property="balanceValue" column="BALANCE_VALUE"/>  
		   <result property="validateTill" column="FROZEN_AT"/>  
		   <result property="cardType" column="TYPE"/>  
		   <result property="isForbidden" column="IS_FORBIDDEN"/>  
		   <result property="alias" column="CARD_ALIAS"/>  
		   <result property="status" column="STATUS"/>
		   <result property="order" column="CARD_ORDER"/>  
    	</collection>[/color]
 
    </resultMap>

<select id="getBailianAmount" parameterType="java.util.Map" resultType="java.math.BigDecimal">
   		
     	 SELECT  
            SUM(BALANCE_VALUE) as BAILIANAMOUNT 
         FROM( 
          SELECT 
            *
          FROM
            AVALIABLE_MEMBER_CARD member
          WHERE
            member.WALLET_ID = [color=red]#{id}[/color]
          UNION
          SELECT 
            *	
          FROM
            AVALIABLE_PRODUCT_CARD product
          where
            product.WALLET_ID = [color=red] #{id}[/color]
          )where TYPE=1 or TYPE=3 
          GROUP BY  WALLET_ID
         
    </select>

association 是对应数据库中一对一的关系，它会将getBailianAmount sql语句的返回值赋给bailianAmount这个属性。column这个属性用于设置getBailianAmount  sql语句的传入参数。column="{id=WALLET_ID}" 意思是将WALLET_ID列作为getBailianAmount sql语句的参数，id对应map的key， sql语句通过#{id}来获取该key的值。