how to prefix a string before sequence generated by postgresql?

Question

This is a sequence

CREATE SEQUENCE technician_id_seq
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE
CACHE 1;

It generates

1

Answer 1

Here are a couple ways:

-- Referencing the sequence directly:
CREATE SEQUENCE test_seq;

SELECT 'AAAA'||nextval('test_seq')::TEXT;
 ?column? 
----------
 AAAA1

SELECT 'AAAA'||nextval('test_seq')::TEXT;
 ?column? 
----------
 AAAA2


-- Using a DEFAULT
CREATE TABLE abc 
    (val TEXT NOT NULL DEFAULT 'AAAA'||nextval('test_seq'::regclass)::TEXT, 
    foo TEXT);

INSERT INTO abc (foo) VALUES ('qewr');

SELECT * FROM abc;
  val  | foo  
-------+------
 AAAA3 | qewr

These assume that you have carefully decided how to proceed, based on the comments to your original question, as asked by the others.