How to sort the result from string_agg()

问题

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.

回答1:

With postgres 9.0+ you can write:

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

Details here.

回答2:

https://docs.microsoft.com/en-us/sql/t-sql/functions/string-agg-transact-sql?view=sql-server-2017

SELECT
  STRING_AGG(prod, '|') WITHIN GROUP (ORDER BY product)
FROM ...

回答3:

select string_agg(prod,' | ') FROM 
  (SELECT product as prod FROM tblproducts ORDER BY product )MAIN;

SQL FIDDLE

来源：https://stackoverflow.com/questions/24906826/how-to-sort-the-result-from-string-agg

标签

sql

postgresql

string-aggregation