PostgreSQL函数返回多个结果集

Question

是否可以从Postgres函数返回多个结果集,如在MSSQL中:

CREATE PROCEDURE test

AS

SELECT * FROM first_table

SELECT * FROM second_table

Answer 1

自PostgreSQL 8.3以来,一种更简单的方法:

CREATE FUNCTION test()
  RETURNS SETOF first_table AS
$func$
BEGIN

RETURN QUERY
SELECT * FROM first_table;

RETURN QUERY
SELECT * FROM second_table;   -- has to return same rowtype as first_table!

END
$func$ LANGUAGE plpgsql;

呼叫:

SELECT * FROM test();

两个结果集都附加到从函数返回的单个集合中.
请参阅手册RETURN QUERY.

Answer 2

CREATE OR REPLACE FUNCTION "pr_GetCustomersAndOrders"()
RETURNS SETOF refcursor AS
$BODY$DECLARE
customerRC refcursor;
orderRC refcursor;
BEGIN
open customerRC FOR
SELECT * FROM customers;
RETURN NEXT customerRC;

open orderRC FOR
SELECT * FROM orders;
RETURN NEXT orderRC;
RETURN;
END;$BODY$
LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION "pr_GetCustomersAndOrders"() OWNER TO postgres;

我喜欢使用refcursors :)

Answer 3

是的。

例子：

test=# create function x () returns setof integer language plpgsql as $$ begin return next 1; return next 2; end $$;
CREATE FUNCTION
test=# select * from x();
 x 
---
 1
 2
(2 rows)

您当然可以使用现有的表/视图或自定义类型作为返回类型。

使用 SQL 语言的示例：

test=# create table customer (name varchar, birth_date date);
CREATE TABLE
test=# create function y () returns setof customer language sql as $$ 
select * from customer
union all
select * from customer
$$;
CREATE FUNCTION
test=# insert into customer values ('joe', now()::date);
INSERT 0 1
test=# insert into customer values ('jill', now()::date);
INSERT 0 1
test=# select * from y();
 name | birth_date 
------+------------
 joe  | 2009-04-16
 jill | 2009-04-16
 joe  | 2009-04-16
 jill | 2009-04-16
(4 rows)

请参阅此处的文档