How to sort the result from string_agg()

Question

I have a table:

CREATE TABLE tblproducts
(
productid integer,
product character varying(20)
)

With the rows:

INSERT INTO tblproducts(productid, product) VALUES (1, 'CANDID POWDER 50 GM');
INSERT INTO tblproducts(productid, product) VALUES (2, 'SINAREST P SYP 100 ML');
INSERT INTO tblproducts(productid, product) VALUES (3, 'ESOZ D 20 MG CAP');
INSERT INTO tblproducts(productid, product) VALUES (4, 'HHDERM CREAM 10 GM');
INSERT INTO tblproducts(productid, product) VALUES (5, 'CREAM 15 GM');
INSERT INTO tblproducts(productid, product) VALUES (6, 'KZ LOTION 50 ML');
INSERT INTO tblproducts(productid, product) VALUES (7, 'BUDECORT 200 Rotocap');

If I execute string_agg() on tblproducts:

SELECT string_agg(product, ' | ') FROM "tblproducts"

It will return the following result:

CANDID POWDER 50 GM | ESOZ D 20 MG CAP | HHDERM CREAM 10 GM | CREAM 15 GM | KZ LOTION 50 ML | BUDECORT 200 Rotocap

How can I sort the aggregated string, in the order I would get using ORDER BY product?

I'm using PostgreSQL 9.2.4.

Answer 1

With postgres 9.0+ you can write:

select string_agg(product,' | ' order by product) from "tblproducts"

Details here.