Two Database Comparisons?

I have two databases called
a) Old Retailer database
b) New Retailer Database

We cant delete old database but we are using and we want to use both of them.

Now problem

Both dbs have a table called retailer.

I want to prevent duplication in them.

I.e it there is a retailer 12 created in old one new one shldnt allowo us to create retailer

id---12

similarly if there is a retailer 13 in new one it shouldnt be created in old table

retailer ids are unique. its not the case that with retailer id for example 5 there is a

different retailer in these two tables of diffferent DBS. Its unique

Now I have to put this criteria

how can i do it?

can any body help me please?


Second questions===================

if a primary key is auto increment. how can i skip some numbers lets say it is 1,2,3,4

i want that when next record shld be inserted it shld be 6 not 5. i dont want to feed the value 6. i want to know how to change indexing of primary key to skip some numbers when its set to auto increments. any help wil be appreciated

Why would you still be creating retailers in the OLD table?

You could create a db link from new to old database and have a trigger check if retailer exists before creating.

can you tell me the sample syntax for creating db link and this trigger

your help will be much appreciated

Is it too difficult for you to check it out in the fine Oracle® Database SQL Language Reference?