如何从string_agg()中对结果进行排序

Question

我有一张桌子:

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

随着行:

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');

如果我执行string_agg()的tblproducts:

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

它将返回以下结果:

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

如何按照我将使用的顺序对聚合字符串进行排序ORDER BY product？

我正在使用PostgreSQL 9.2.4.

Answer 1

使用postgres 9.0+,你可以写:

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

详细信息:http://www.postgresql.org/docs/current/static/sql-expressions.html#SYNTAX-AGGREGATES

Answer 2

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

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