高手求一SQL语句，高手请进！！！！！！！

[kingyond]

表一，客户表customer
customer_id number(10) //客户ID，索引，无重复
customer_link_id number(10) //客户首选联系人
表二，客户联系人列表 customer_link
customer_link_id number(10)//客户ID，索引，无重复
customer_name varchar2(100)//客户选联系人
customer_id number(10)
假定表一数据如下，
customer_id customer_link_id
1001 2001
1002 0 //没有首选联系人
1003 2002
表二数据如下
customer_link_id customer_link_name customer_id
2001 csdn 1001
2002 www.taneipc.net 1001
2003 iloveu 1002
求一条sql语句返回以下结果:
customer_id customer_link_name
1001 csnd
1002 empty//为空
1003 www.taneipc.net

问题就出在首选联系人为空的时候
我开始是用以下select语句的：
select customer.customer_id,customer_link_name from
customer left jion customer_link on
customer.customer_link_id=customer_link.customer_link_id
结果可以返回选择
但是返回 customer_link_name 首选联系人为空处错误（变为非空值）。
每二次改为:
select customer.customer_id,customer_link_name from
customer left jion (select customer_link.customer_link_id,customer_link,customer_link_name
from customer_link inner join customer on customer.customer_link_id=customer_link.customer_link_id) on
customer.customer_link_id=customer_link_id
结果可以返回，但是出错地方依旧。
请高手指点？？？？？？？？？？？？？？？？？

[kingyond]

表二写错了，以下为更正后的内容
表二，客户联系人列表 customer_link
customer_link_id number(10)//客户联系人ID，索引，无重复
customer_link_name varchar2(100)//客户联系人名字
customer_id number(10) //表一中的ID

[xiaodongisme]

SELECT a.customer_id,b.customer_link_name FROM customer a,customer_link b
WHERE a.customer_link_id = b.customer_link_id(+)
ORDER BY a.customer_id

[skystar99047]

select a.customer_id,nvl(b.customer_link_name,'无') from
customer a,customer_link b where a.customer_link_id=b.customer_link_id(+);

[xinpingf]

高手求sql语句

[beckhambobo]

select a.customer_id,nvl(b.customer_link_name,'empty') from
customer a,customer_link b where a.customer_link_id=b.customer_link_id(+);

[kingyond]

谢谢三位!结贴啦！

[kingyond]

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