子查询返回的多行用作表达式但仅在函数中答案

【问题标题】：More than one row returned by a subquery used as an expression but only in function子查询返回的多行用作表达式但仅在函数中
【发布时间】：2020-11-14 05:03:46
【问题描述】：

当我使用一个函数时，它给出了提到的错误，但是当单独使用相同的代码时它工作得很好。问题出在哪里？

使用函数：https://dbfiddle.uk/?rdbms=postgres_12&fiddle=c4b0c8a59d2bd851284ed624ab1c335d

使用干净选择填充：https://dbfiddle.uk/?rdbms=postgres_12&fiddle=7ccca6c70061aff1f6c394815aa8e9b1

样本数据：

create table report
(report_day date,
 tickets_no integer,
 tickets_stake numeric,
 promo_tickets_no integer,
 promo_tickets_stake numeric,
 group_id integer);
 
 insert into report
 values
 ('2020-07-20',12,569.6, 2, 44,1),
 ('2020-07-20',61,2000, 5, 260,2),
  ('2020-07-21',35,1244.2, 11, 250,1),
  ('2020-07-21',100,2500.5, 29, 575,2),
   ('2020-07-22',66,2511.8, 23, 670,1),
   ('2020-07-22',125,3358.2, 50, 990,2);

CREATE OR REPLACE FUNCTION report(arguments json)
  RETURNS json AS
$BODY$
     
DECLARE 
        
    dateFrom date;
    dateTo date;
        selectedType integer;
BEGIN 
        
    dateFrom := cast(arguments->>'dateFrom' as date);
    dateTo := cast(arguments->>'dateTo' as date);
    selectedType := cast(arguments->>'selectedType' as integer);

RETURN (
    WITH full_data as (
 with tickets as (
  select 
    report_day
  , sum(tickets_no) as tickets_no
  , sum(tickets_stake) as tickets_stake
  FROM report
  WHERE selectedType = 0
  AND report_day between dateFrom and dateTo
  GROUP BY 1)
  
, promo_tickets as (
  select 
    report_day
  , sum(promo_tickets_no) as promo_tickets_no
  , sum(promo_tickets_stake) as promo_tickets_stake
  FROM report
  WHERE selectedType = 1
  AND report_day between dateFrom and dateTo
  GROUP BY 1)
  
  select 
    t.report_day 
  , sum(coalesce(t.tickets_no,0) + coalesce(pt.promo_tickets_no,0)) as tickets_no                             
  , sum(coalesce(t.tickets_stake,0) + coalesce(pt.promo_tickets_stake,0)) as tickets_no
  FROM tickets t
  LEFT JOIN promo_tickets pt on t.report_day = pt.report_day                                    
   GROUP BY 1
   ORDER BY 1)
        
select row_to_json(full_data) from full_data
);

END;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
  
  select * from report(json_build_object('dateFrom', '2020-07-20', 'dateTo', '2020-07-22','selectedType', 0 ))

【问题讨论】：

标签： sql postgresql stored-functions

【解决方案1】：

因为您试图从一个应该只返回一行的函数返回多行。向您的函数添加一个参数，最好是主键列（我想是tickets_no），例如

CREATE OR REPLACE FUNCTION report(arguments json, i_tickets_no int)

并将查询重写为

WITH full_data AS
 (WITH tickets AS
     (SELECT report_day,
            SUM(tickets_no) AS tickets_no,
            SUM(tickets_stake) AS tickets_stake
       FROM report
      WHERE selectedType = 0
        AND report_day BETWEEN dateFrom AND dateTo
        AND tickets_no = i_tickets_no
      GROUP BY 1),
    promo_tickets as
     (select report_day,
            SUM(promo_tickets_no) as promo_tickets_no,
            SUM(promo_tickets_stake) as promo_tickets_stake
       FROM report
      WHERE selectedType = 1
        AND report_day BETWEEN dateFrom AND dateTo
      GROUP BY 1)
    
    select t.report_day,
           SUM(COALESCE(t.tickets_no, 0) + COALESCE(pt.promo_tickets_no, 0)) AS tickets_no,
           SUM(COALESCE(t.tickets_stake, 0) +
               COALESCE(pt.promo_tickets_stake, 0)) AS tickets_no
      FROM tickets t
      LEFT JOIN promo_tickets pt
        ON t.report_day = pt.report_day
     GROUP BY 1
     ORDER BY 1)

并通过添加第二个参数来调用。

Demo

【讨论】：

【解决方案2】：

如果您希望函数像查询一样返回报表对象数组，请更改此部分：

select row_to_json(full_data) from full_data

将行聚合成一个数组：

select json_agg(row_to_json(full_data)) from full_data

如果希望函数返回多行，则需要进行两处更改：

CREATE OR REPLACE FUNCTION report(arguments json)
  RETURNS table (row_to_json json) AS

对于return：

RETURN QUERY (
    WITH full_data as (

更新fiddle here.

【讨论】：

不可以返回多个json行吗？
@sh4rkyy 如果您的函数返回类型是json，则不是。请查看我的答案的更新。