How to auto-increment in PostgreSQL ?

Question

I have a table Login. It has the fields rank, username and password.

I want the rank gets auto incremented with respect to addition of username and password.

How do I do this in PostgreSQL ?

Answer 1

You are looking for a column with datatype Serial. See this page (bottom) for more information about that datatype.

So for example, your table definition could look like this:

CREATE TABLE yourtable (
    rank SERIAL NOT NULL,
    username VARCHAR(20) NOT NULL,
    password VARCHAR(50) NOT NULL
);

Answer 2

create table login (rank serial, username varchar(20), password varchar(20))

Serial datatype is what you want.

Answer 3

A Sequence can be created which will auto increment the value of rank column.

CREATE SEQUENCE rank_id_seq;

CREATE TABLE yourtable ( rank INTEGER NOT NULL default nextval('rank_id_seq'), username VARCHAR(20) NOT NULL, password VARCHAR(50) NOT NULL );

ALTER SEQUENCE rank_id_seq owned by yourtable.rank;