Default Primary Key Field of any database table

Question

hi,
I am working on a database in which the data in the tables is generated from some other modules. I have to add, view and update functionalities to this table in the database. Unfortunately there is no primary key field for the table i am working on and as some existing modules are using this table i am not allowed to change the design of the table at this stage.
Without primary i think its not possible to do updates. Because if all fields can have their values changed, then there will be a breakdown if the field value changes in the mid time when i had already retrieved the data to show on the screen, but not yet updated the value in the database. I hope you understood my problem.
Please suggest solutions. I am not sure, but i think i read somewhere that every table created has a default primary associated whose value is always incresing with a new addtion of recored and its value never decreases. But i am unable to recollect the field name...i think it is some thing like[b] OID .... But i checked there is no such field name by OID. So please help me with some alternative solution...or by telling the default primary key field name.
Thanx

Answer 1

All the databases I know (namely Informix, PostgreSQL, SQL Server, even Access) have a row id column generated automatically.
PostgreSQL example
There is a way to read the value of this column; for example with PostgreSQL let�s say you have the following:
CREATE TABLE no_id_column (
column_one varchar(80),
column_two varchar(80)
INSERT INTO no_id_column(column_one, column_two) VALUES (�red�, �pink�);
INSERT INTO no_id_column(column_one, column_two) VALUES (�yellow�, �orange�);Certainly, if we executed:
SELECT * FROM no_id_column;Would obtain:
column_one          column_two
red               pink
yellow               orangeBut if we modify the query
SELECT  oid, * FROM no_id_column;We magically obtain a row identificator
oid          column_one          column_two
21569          red               pink
21570          yellow               orangeThe data in the oid column is generated automatically by the database manager. Every time we insert a row we�ll have a different one. Just take into account that if the database contains a large amount of data, the oid could cycle.