Postgresql将多行查询结果赋值给变量并继续执行

Question

我正在尝试创建一个脚本来调用 PostgreSQL 中的多个存储过程并打印其中一些的结果：

CREATE OR REPLACE FUNCTION script(
vtoken character varying) 
  RETURNS void AS
$BODY$
DECLARE
  aux character varying;
BEGIN

PERFORM (SELECT acquire_table(vtoken));

-- This query gets the dynamically generated token for the client in that codebar
aux := (SELECT token 
                FROM clients c JOIN tables t ON c.tablekey = t.tablekey 
                WHERE codebar = vtoken);

PERFORM (SELECT order_drinks(aux, '{1}', '{1}'));

--EXECUTE (SELECT issue_ticket(aux));

PERFORM (SELECT order_drinks(aux, '{1}', '{1}'));


END;$BODY$
  LANGUAGE plpgsql VOLATILE

issues_ticket() 函数返回多行结果，我想直接打印它并继续执行下一个函数（order_drinks()）。如果我执行 PERFORM，它不会显示结果，如果我只是尝试按原样执行 SELECT 查询，它会要求将返回值分配给变量。

Answer 1

通常的方法是使用返回行集returns table。然后调用该函数的客户端可以打印它。该函数本身在return. 例如：

create or replace function script() 
RETURNS TABLE (col1 int)
language plpgsql
as $_$ begin
RETURN QUERY (VALUES (6), (7), (6*7));
RAISE NOTICE 'continuing after return';
end;
$_$;
select * from script();

这打印：

NOTICE:  continuing after return
 col1 
------
    6
    7
   42
(3 rows)

您还可以将函数的结果存储在（临时）表中：

create or replace function script2() 
returns table (col1 int)
language plpgsql
as $_$ 
begin
CREATE TEMPORARY TABLE temp_table (id int) ON COMMIT DROP;
INSERT INTO temp_table SELECT * FROM script();
return query (select * from temp_table);
end;
$_$;
select * from script2();

这打印：

NOTICE:  continuing after return
CONTEXT:  SQL statement "insert into temp_table select * from script() s where s.col1 < 42"
PL/pgSQL function script2() line 4 at SQL statement
 col1 
------
    6
    7
(2 rows)