Primary & Foreign Keys in pgAdmin

Question

I was wondering can some give me an explanation on how to assign primary and foreign keys in pgAdmin?

I can\'t find any information online.

For example...I\'ve g

Answer 1

There is no option in pgAdmin to add a column to an existing table and make it the primary key at the same time, because this is hardly possible.

A primary key column needs to hold unique non-null values. Upon adding a column to an existing table, it holds NULL values. So you have to enter unique values before you can add a UNIQUE or PRIMARY KEY constraint.

There is an exception to that rule, though: If you add a serial column, unique values are inserted automatically. In this case, you can also define it PRIMARY KEY right away:

ALTER TABLE student ADD COLUMN student_number serial PRIMARY KEY;

This works in PostgreSQL 9.1. I am not sure it does in older versions, too.

pgAdmin does not incorporate this special case for serial columns in the "New column..." dialog at this time (version 1.14).