postgresql - 在函数中使用 plpgsql 复制到 csv 的动态 csv 文件导出错误

Question

我正在尝试过滤 postgresql 表以查找将产品 ID 作为外键的行。对于每个产品 ID，我需要分别将 1 个 csv 导出到一个文件夹，例如 prod1.csv、prod2.csv 等。我试图创建下面的函数来自动执行此操作，但是当我运行它时该函数失败了。任何人都可以帮助我修复功能或推荐更好的方法吗？

CREATE or replace FUNCTION exportdata() 
RETURNS SETOF record AS
$$
DECLARE
 rec text;
BEGIN
 FOR rec IN 
(
Select distinct t.products from trndailyprices as t --Get the list of products in the table
) 
 LOOP
    Copy (
    Select * from trndailyprices as t
    where t.products = rec   ---1st record is product1
    order by t.effectivedate) 
    To 'C:/testQ/' ||rec || '.csv' With CSV;---expected file is product1.csv for 1st record
 END LOOP;
END;
$$ LANGUAGE plpgsql;

Answer 1

试试这个

CREATE or replace FUNCTION exportdata() 
RETURNS void AS -- use void because you're not returning anything 
$$
DECLARE
 rec text;
BEGIN
 FOR rec IN 
Select distinct t.products from trndailyprices as t 
 LOOP
EXECUTE -- you need to use EXECUTE Keyword 
    format('Copy (
    Select * from trndailyprices as t
    where t.products =''%s''
    order by t.effectivedate) 
    To ''C:/testQ/%s.csv'' With CSV;',rec,rec);
 END LOOP;
END;
$$ LANGUAGE plpgsql;

---

修改:

create or replace function exportdata_1() returns void as 
$$
declare
rec record;
begin
for rec in
select format('copy(select * from trndailyprices where products=''%s'') to ''%s'' with csv',product,'D:/testQ/'||product||'.csv;') scr from(
Select distinct products from trndailyprices )t
loop
execute rec.scr;
end loop;
end;
$$
language plpgsql