如何return只有一行一列的名字？

Question

正在自学Psql函数，想return只有一行一列名：dep_people不知道如何一行一解决这道题列名称。请帮我理解Psql函数。

预览table

SELECT * FROM test_sch.apollo_org_job_function;

|-------------------------------------------|
|organization_id |department      |no_people|
|-------------------------------------------|
|      2a        |accounting      |   3     | 
|      1a        |engineering     |   2     |
|      1a        |entrepreneurship|   1     | 
|      1a        |human resources |   4     |
|-------------------------------------------|

我在这里

SELECT
    department, no_people
FROM test_sch.apollo_org_job_function 
GROUP BY department, no_people 
ORDER BY department;

我的return是：

|--------------------------|
|department      |no_people|
|--------------------------|
|accounting      |  3      | 
|engineering     |  2      |
|entrepreneurship|  1      | 
|human resources |  4      |
|--------------------------|

调用函数

select * from test_sch.return_dep_people('1a')
as f(dep_people text);

预期输出

------------------------------------------------------|
|dep_people                                           |
------------------------------------------------------|
|Engineering:2 , human_resources:4, entrepreneurship:1| 
-------------------------------------------------------

注意：结果应该只包含 1 个名为“dep_people”的列和字符串中的 1 行，“Engineering:2，human_resources:4，entrepreneurship:1”是一个字符串)

Answer 1

您可以使用 JSON_BUILD_OBJECT 和 JSON_AGG 实现此目的：

WITH data AS (
  SELECT department, COUNT(*) as "no_people"
  FROM apollo_org_job_function GROUP BY department ORDER BY department
) SELECT 
    JSON_AGG(JSON_BUILD_OBJECT(department, no_people)) as "dep_people"
FROM data;

PostgreSQL JSON_AGG JSON_BUILD_OBJECT

Answer 2

我想，STRING_AGG 可能会对您有所帮助。像这样：

SELECT
  STRING_AGG(d.department || ': ' || CAST(d.no_people AS text), ', ') AS dep_people 
FROM ([your initial query]) AS d

Answer 3

create function happy_return_dep_people(organisation_id text)
returns text
language plpgsql
as
$$
declare
   dep_people text;
begin
      SELECT STRING_AGG(d.department || ': ' || CAST(d.no_people AS text), ', ') into dep_people AS dep_people 
      FROM (
        SELECT department, no_people
      FROM test_sch.apollo_org_job_function
      WHERE organization_id = organisation_id
      GROUP BY department, no_people ORDER BY department) AS d;
   
   return dep_people;
end;
$$;

select * from test_sch.happy_return_dep_people('1a') 
as dep_people;

如何return只有一行一列的名字？

How to return only one row and one column name?

sql

postgresql

aggregate-functions