请教一条sql查询语句,在线等,谢谢大家的帮忙
create table testSomething(
userid varchar(16),--人员编号
cardid int ,--出生证号码
isUsing int,--是否作废 1在使用,2已作废
timeChange datetime --作废时间
);
insert into testSomething(userid,cardid,isUsing) values('22',1111,1);
insert into testSomething(userid,cardid,isUsing,timeChange) values('22',2222,2,'2010-09-14 15:28:55.577');
insert into testSomething(userid,cardid,isUsing) values('33',3333,1);
insert into testSomething(userid,cardid,isUsing,timeChange) values('33',4444,2,'2010-09-16 15:28:55.577');
insert into testSomething(userid,cardid,isUsing,timeChange) values('33',5555,2,'2010-09-17 15:28:55.577');
insert into testSomething(userid,cardid,isUsing) values('44',6666,1);
--------查询结果,人员编号,出生证编号,变更前的出生证编号(最近作废的那个),没有变更的,显示空值
人员编号 出生证编号,变更前的出生证编号
22 1111 2222
33 3333 5555
44 6666