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rox — Wed, 23 Apr 2008 09:33:00 GMT

�q�两句SQL区别是有没有括号�Q�但却是一个可以查出来�Q�一个几乎查不出来�?br /> 一个简单的问题�Q�居然还犯低�U�错误，留下来提醒自己�?/p>

1select uj.* from union_job uj , union_company uc where (uj.name like '%职员%' or uj.info like '%职员%') and uj.company_id=uc.id and uc.area= '�q�东' order by uj.uptime desc

1select uj.* from union_job uj , union_company uc where uj.name like '%职员%' or uj.info like '%职员%' and uj.company_id=uc.id and uc.area= '�q�东' order by uj.uptime desc

rox 2008-04-23 17:33 发表评论

MySql中集合运��非常规实现

rox — Fri, 01 Sep 2006 01:29:00 GMT

MySql只支持Union(�q��)集合�q�算�Q�好像也�?.0以后才有的；
但是对于交集Intersect、差集Except�Q�就没有实现了�?br />一般的解决�Ҏ��用in和not in来解冻I��量数据�q�可以，但数据量大了效率��很低了�?br />其实�Q�可以��用Union来实现另外两�U�的�q�算�Q�当然是没有办法的办法�?br />
差集Except:
SELECT ID FROM (
SELECT DISTINCT A.AID AS ID FROM TABLE_A A
UNION ALL
SELECT DISTINCT B.BID AS ID FROM TABLE_B B
)TEMP GROUP BY ID HAVING COUNT(ID) = 1

交集Intersect:
SELECT ID FROM (
SELECT DISTINCT A.AID AS ID FROM TABLE_A A
UNION ALL
SELECT DISTINCT B.BID AS ID FROM TABLE_B B
)TEMP GROUP BY ID HAVING COUNT(ID) = 2

不过�Q�上�q�方法的功能也有限，
只能用来��查某个id是不是A、B表中都存在，
或者只存在于A、B表其中之一�Q?br />�q�不能对id在某表中多次出现做出��查�?br />而且�Q�差集是有先后之分，�q�里没有�?br />

rox 2006-09-01 09:29 发表评论

Oracle集群的URL�~�写

rox — Wed, 07 Jun 2006 01:04:00 GMT

1、首先制作一个批处理�Q�对集群IP�q�行DNS讄��Q?br />

1 @echo off
2 if not exist hosts goto WNT
3 echo 192.168.2.5 HIS_S0 >>C:\windows\hosts
4 echo 192.168.2.6 HIS_S1 >>C:\windows\hosts
5 goto END
6 :WNT
7 echo 192.168.2.5 HIS_S0 >>%systemroot%\system32\drivers\etc\hosts
8 echo 192.168.2.6 HIS_S1 >>%systemroot%\system32\drivers\etc\hosts
9 :END
10 echo Finished!
11 pause > nul
12 cls

2、配�|�一个URL来连接这个集��，集群的服务名为HIS�Q?br />

1 jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=HIS_S0)(PORT=1521))(ADDRESS=(PROTOCOL=TCP)(HOST=HIS_S1)(PORT=1521))(LOAD_BALANCE=yes))(CONNECT_DATA=(SERVICE_NAME=HIS)))

rox 2006-06-07 09:04 发表评论

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MySql中集合运���非常规实现

Oracle集群的URL�~�写

MySql中集合运��非常规实现