PostgreSQL函数中如何返回查询结果行？

我按照教程尝试了很多次，但都失败了。 有人可以给我一些例子吗？ 这是我的代码，它提示“ERROR:invalid type name 'SETOF RECORD'”

create or replace function find() returns SETOF RECORD
as $$
declare A SETOF RECORD;
begin
    A=(
        select x,y
        from .......

    )
    CASE WHEN EXISTS A 
    THEN returns query A
    ELSE returns query (
        select x,y
        from ......
    )
    END;

end;
$$ language plpgsql;

我目前记得的声明集合返回函数的方法：

--example 1
create or replace function test() returns SETOF RECORD
as $$
begin
    RETURN QUERY SELECT * FROM generate_series(1,100);
end;
$$ language plpgsql;
--test output
select * from test() AS a(b integer)

--example 2
create or replace function test2() returns TABLE (b integer)
as $$
begin
    RETURN QUERY SELECT * FROM generate_series(1,100);
end;
$$ language plpgsql;
--test output
select * from test2()

--example 3
create or replace function test3() returns SETOF RECORD
as $$
declare
  r record;
begin
    FOR r IN SELECT * FROM generate_series(1,100) LOOP
      RETURN NEXT r;
    END LOOP;
end;
$$ language plpgsql;
--test output
select * from test3() AS a(b integer);

--example 4
create or replace function test4() returns setof record
as $$
    SELECT * FROM generate_series(1,100)
$$ language sql;
--test output
select * from test4() AS a(b integer);

--example 5
create or replace function test5() returns setof integer
as $$
begin
    RETURN QUERY SELECT * FROM generate_series(1,100);
end;
$$ language plpgsql;
--test output
select * from test5()

--example 6
create or replace function test6(OUT b integer, OUT c integer) RETURNS SETOF record
as $$
begin
    RETURN QUERY SELECT b.b, b.b+3 AS c FROM generate_series(1,100) AS b(b);
end;
$$ language plpgsql;
--test output
select * from test6()