java中关联查询对象中的对象属性,连接表查询最好用左连接(左表作为主表)
好处:主表中某些记录与关联表不满足连接查询条件时，查询结果不会丢失主表的数据
例：
SELECT
    a.domainId,
    a. NAME,
    a.systemName,
    a.ip,
    a. PORT,
    a. STATUS,
    a.description,
    a.orgnizationdoc_id AS "org.id",
    b. NAME AS "org.name",
    a.applyBy AS "applyBy.userId",
    a.applyDate,
    a.applyInfo,
    a.approveBy AS "approveBy.userId",
    a.approveDate,
    a.approveInfo,
    c. NAME AS "applyBy.name" d. NAME AS "approveBy.name"
FROM
    net_domain_tbl a
JOIN cod_orgnizationdoc_tbl b ON a.orgnizationdoc_id = b.id
LEFT JOIN sys_user_tbl c ON a.applyBy = c.userId
LEFT JOIN sys_user_tbl d ON a.approveBy = d.userId
WHERE
    a.orgnizationdoc_id = #{org.id} and a.status >='1'