ibatis的官方示例请教

Question

JPetStore5.0的示例  这样的写法有什么好处？SQL语句执行的几遍？ 本人新手望各位大侠详细解答  小弟谢谢了

<typeAlias alias="account" type="com.ibatis.jpetstore.domain.Account"/>

  <select id="getAccountByUsername" resultClass="account" parameterClass="string">
    SELECT
          SIGNON.USERNAME,
          ACCOUNT.EMAIL,
          ACCOUNT.FIRSTNAME,
          ACCOUNT.LASTNAME,
          ACCOUNT.STATUS,
          ACCOUNT.ADDR1 AS address1,
          ACCOUNT.ADDR2 AS address2,
          ACCOUNT.CITY,
          ACCOUNT.STATE,
          ACCOUNT.ZIP,
          ACCOUNT.COUNTRY,
          ACCOUNT.PHONE,
          PROFILE.LANGPREF AS languagePreference,
          PROFILE.FAVCATEGORY AS favouriteCategoryId,
          PROFILE.MYLISTOPT AS listOption,
          PROFILE.BANNEROPT AS bannerOption,
          BANNERDATA.BANNERNAME
    FROM ACCOUNT, PROFILE, SIGNON, BANNERDATA
    WHERE ACCOUNT.USERID = #username#
      AND SIGNON.USERNAME = ACCOUNT.USERID
      AND PROFILE.USERID = ACCOUNT.USERID
      AND PROFILE.FAVCATEGORY = BANNERDATA.FAVCATEGORY
  </select>

Answer 1

不知道你具体哪里不明白？
难道是这个多表关联的sql语句查询不明白？
语句只被执行一次，然后由数据库将语句解析处理。