在 postgreSQL 中使用 string_agg 将两行连接成一行，逗号分隔

Question

clique_bait.page_hierarchy

CREATE TABLE clique_bait.page_hierarchy (
  "page_id" INTEGER,
  "page_name" VARCHAR(14),
  "product_category" VARCHAR(9),
  "product_id" INTEGER
);
sample input 
  ('1', 'Home Page', null, null),
  ('2', 'All Products', null, null),
  ('3', 'Salmon', 'Fish', '1'),
  ('4', 'Kingfish', 'Fish', '2'),
  ('5', 'Tuna', 'Fish', '3'),
  ('6', 'Russian Caviar', 'Luxury', '4'),
  ('7', 'Black Truffle', 'Luxury', '5'),

clique_bait.events

CREATE TABLE clique_bait.events (
  "visit_id" VARCHAR(6),
  "cookie_id" VARCHAR(6),
  "page_id" INTEGER,
  "event_type" INTEGER,
  "sequence_number" INTEGER,
  "event_time" TIMESTAMP
);

sample input: 
  ('ccf365', 'c4ca42', '1', '1', '1', '2020-02-04 19:16:09.182546'),
  ('ccf365', 'c4ca42', '2', '1', '2', '2020-02-04 19:16:17.358191'),
  ('ccf365', 'c4ca42', '6', '1', '3', '2020-02-04 19:16:58.454669'),
  ('ccf365', 'c4ca42', '9', '1', '4', '2020-02-04 19:16:58.609142'),
  ('ccf365', 'c4ca42', '9', '2', '5', '2020-02-04 19:17:51.72942'),
  ('ccf365', 'c4ca42', '10', '1', '6', '2020-02-04 19:18:11.605815'),
  ('ccf365', 'c4ca42', '10', '2', '7', '2020-02-04 19:19:10.570786'),
  ('ccf365', 'c4ca42', '11', '1', '8', '2020-02-04 19:19:46.911728'),
  ('ccf365', 'c4ca42', '11', '2', '9', '2020-02-04 19:20:45.27469'),
  ('ccf365', 'c4ca42', '12', '1', '10', '2020-02-04 19:20:52.307244'),
  ('ccf365', 'c4ca42', '13', '3', '11', '2020-02-04 19:21:26.242563'),
  ('d58cbd', 'c81e72', '1', '1', '1', '2020-01-18 23:40:54.761906'),
  ('d58cbd', 'c81e72', '2', '1', '2', '2020-01-18 23:41:06.391027'),
  ('d58cbd', 'c81e72', '4', '1', '3', '2020-01-18 23:42:02.213001'),
  ('d58cbd', 'c81e72', '4', '2', '4', '2020-01-18 23:42:02.370046'),
  ('d58cbd', 'c81e72', '5', '1', '5', '2020-01-18 23:42:44.717024'),
  ('d58cbd', 'c81e72', '5', '2', '6', '2020-01-18 23:43:11.121855'),
  ('d58cbd', 'c81e72', '7', '1', '7', '2020-01-18 23:43:25.806239'),
  ('d58cbd', 'c81e72', '8', '1', '8', '2020-01-18 23:43:40.537995'),
  ('d58cbd', 'c81e72', '8', '2', '9', '2020-01-18 23:44:14.026393'),
  ('d58cbd', 'c81e72', '10', '1', '10', '2020-01-18 23:44:22.103768'),
  ('d58cbd', 'c81e72', '10', '2', '11', '2020-01-18 23:45:00.004781'),
  ('d58cbd', 'c81e72', '12', '1', '12', '2020-01-18 23:45:38.186554')

clique_bait.event_identifier

CREATE TABLE clique_bait.event_identifier (
  "event_type" INTEGER,
  "event_name" VARCHAR(13)
);

Sample input
  ('1', 'Page View'),
  ('2', 'Add to Cart'),
  ('3', 'Purchase'),
  ('4', 'Ad Impression'),
  ('5', 'Ad Click');

我需要的输出是 Visit_id、Page_name 添加到购物车并用逗号连接

我的查询

select visit_id, string_agg(page_name::character varying, ',') 
within group (order by sequence_number) as cart_items                        
from clique_bait.events e 
join clique_bait.page_hierarchy ph 
on e.page_id = ph.page_id 
join clique_bait.event_identifier ei 
on ei.event_type = e.event_type
where event_name = 'Add to Cart'
group by visit_id

不工作，错误：函数 string_agg（字符变化，未知，整数）不存在

Answer 1

试一试：

select visit_id, string_agg(page_name, ',' order by sequence_number) as cart_items                        
from events e 
join page_hierarchy ph on e.page_id = ph.page_id 
join event_identifier ei on ei.event_type = e.event_type
where event_name = 'Add to Cart'
group by visit_id

string_agg(...) 函数中的 order by sequence_number 将根据序列号对逗号分隔的输出进行排序。

以下是您提供的示例数据的示例： https://dbfiddle.uk/?rdbms=postgres_13&fiddle=52077d5be605a51d3a7bb14152a392df

结果如下：

visit_id | cart_items   
:------- | :------------
d58cbd   | Kingfish,Tuna

在 postgreSQL 中使用 string_agg 将两行连接成一行，逗号分隔

Concatenate few rows into a single row with comma seperated using string_agg in postgreSQL

postgresql

concatenation

string-agg