Which data type to use to reference SERIAL data type in PostgreSQL?

Question

I have two tables in PostgreSQL. The first one should have an auto-incrementing ID field that the second one references:

CREATE TABLE tableA (id SERIAL NOT NULL          


        

Answer 1

A serial is an integer and it's not "unsigned". The sequence that is created automatically just happens to start at 1 - that's all. The column's data type is still an integer (you could make the sequence start at -2147483648 if you wanted to).

Quote from the manual

CREATE TABLE tablename (
    colname SERIAL
);

is equivalent to

CREATE SEQUENCE tablename_colname_seq;
CREATE TABLE tablename (
    colname integer NOT NULL DEFAULT nextval('tablename_colname_seq')
);
ALTER SEQUENCE tablename_colname_seq OWNED BY tablename.colname;

(emphasis mine)