Question

In PostgreSQL I have table comments with primary key comment_id (VARCHAR of length 4). I have a form to insert a comment. How to get my Java Servlet to increment comment_id for each INSERT (0001 to 0002)?

Answer 1

You don’t want to use a VARCHAR for your id column. In postgres you can create a sequence and then get the next value of that sequence for each insert.

here are the docs

Basically, you do something like

CREATE SEQUENCE mysequence START 101

Then, when you insert you do something like

INSERT INTO my_comment values (nextval('mysequence'), 'this is my comment');