怎样把两条SQL写成一条语句
select session.* from hacref.session,hacconf.user,hacconf.orgunit where session.username=user.username and user.ou_id=orgunit.id and (orgunit.ou_id&(select ou_id from hacconf.orgunit where id=4))=(select ou_id from hacconf.orgunit where id=4);
 
select session.* from hacref.session,hacconf.device,hacconf.orgunit where serverIP=device.ip and device.ou_id=orgunit.id and (orgunit.ou_id&(select ou_id from hacconf.orgunit where id=4))=(select ou_id from hacconf.orgunit where id=4);

有两条语句，分别根据username,serverTP过滤条件，我想实现两者同时过滤，直接两条件AND会是空，需要帮助

------解决方案--------------------
有是有这种语法，只是语句写的貌似不合理，特别是最后=（select ... where id=4）那段，比较危险，一旦没控制好，数据出现2条以上就报错了，而且两个查询的表都不一样，合并不了的，要么就用union all合起来。
------解决方案--------------------
union 本身就会过滤重复数据。还有except这些也是可以过滤重复数据的，不知道你要怎么过滤。你自己看看联机丛书
------解决方案--------------------

SQL code

SELECT A1.* 
FROM hacref.session AS A1 
JOIN hacconf.user AS A2 ON (A1.username=A2.username)
JOIN hacconf.orgunit AS A3 ON (A2.ou_id=A3.ID) 
JOIN hacconf.device AS A4 ON (A1.serverIP=A4.IP AND A4.OU_ID=A3.ID)

WHERE (A3.OU_ID & (select ou_id from hacconf.orgunit where id=4)) = 
(select ou_id from hacconf.orgunit where id=4)

------解决方案--------------------
首先是两条合并  考虑union    而不是or或者and  但从字意上理解就可以区别出来   使用union 必须将两个sql语句的 列数量保持一致  ，写代码细心很重要 ，