In Postrges, I know how to create a table with a column that has a serial (number) id:
CREATE TABLE Tag (
id SERIAL PRIMARY KEY,
name TEXT NOT NULL
);
I prefer to have my ids have a human readable aspect to them though. I usually do something like tag_1, tag_2, tag_3 usr_1, usr_2, usr_3.
I've seen instructions on how to generate uuids (Generating a UUID in Postgres for Insert statement?), but I don't really need that. The basic serial number is more than enough, I just want to prefix tag_ to the beginning.
How can I create a Serial ID with as a string with common prefix?
You can do that with a sequence, which you can add to your table as a default value concatenated via || with the prefix you want e.g.
CREATE SEQUENCE tag_seq START WITH 1;
CREATE TABLE tag
(id TEXT NOT NULL DEFAULT 'tag_'||nextval('tag_seq'::regclass),
name TEXT);
INSERT INTO tag (name) VALUES ('foo'),('bar');
SELECT * FROM tag;
id | name
-------+------
tag_1 | foo
tag_2 | bar
(2 Zeilen)
Demo: db<>fiddle