using UID/Pass in a query with a public database link

I have a public database link that doesn't have any uid/pass mentioned. I need to use it in a query but after giving uid/pass.

Something like, select * from uid/pass.tbl_comp@lin开发者_运维问答k_name

what can i do?

As you said,there was no UID and Pass given for a Database Link,then you can use that link as Connected SYSTEM user,where Connected user is defined as:

Connected User: A local user accessing a database link in which no fixed username and password have been specified. If SYSTEM accesses a public link in a query, then the connected user is SYSTEM, and the database connects to the SYSTEM schema in the remote database. Note: A connected user does not have to be the user who created the link, but is any user who is accessing the link.

And there are other type of Users category who can use the same link by supplying different parameters while querying the database link,for which you can further read on for usage of Select command with DB link at bottom of this link page: http://download.oracle.com/docs/cd/B28359_01/server.111/b28310/ds_concepts002.htm

Some Description about Database Link,if you read this before,then please ignore it:

Database Link: A database link connection is one-way in the sense that a client connected to local database A can use a link stored in database A to access information in remote database B, but users connected to database B cannot use the same link to access data in database A. If local users on database B want to access data on database A, then they must define a link that is stored in the data dictionary of database B.

A database link connection allows local users to access data on a remote database. For this connection to occur, each database in the distributed system must have a unique global database name in the network domain. The global database name uniquely identifies a database server in a distributed system.

Example:-