以下主要介紹PostgreSQL函式/儲存過程返回資料集，或者也叫結果集的示例。 

背景： PostgreSQL裡面沒有儲存過程，只有函式，其他資料庫裡的這兩個物件在PG裡都叫函式。 函式由函式頭，體和語言所組成，函式頭主要是函式的定義，變數的定義等，函式體主要是函式的實現，函式的語言是指該函式實現的方式，目前內建的有c,plpgsql,sql和internal,可以通過pg_language來檢視當前DB支援的語言，也可以通過擴充套件來支援python等 

函式返回值一般是型別，比如return int,varchar，返回結果集時就需要setof來表示。 

一、資料準備

create table department(id int primary key, name text);
create table employee(id int primary key, name text, salary int, departmentid int references department);

insert into department values (1, 'Management'),(2, 'IT'),(3, 'BOSS');

insert into employee values (1, 'kenyon', 30000, 1);
insert into employee values (2, 'francs', 50000, 1);
insert into employee values (3, 'digoal', 60000, 2);
insert into employee values (4, 'narutu', 120000, 3);

create or replace function f_get_employee() 
returns setof employee 
as 
$$
select * from employee;
$$
language 'sql';

create or replace function f_get_employee_query() 
returns setof employee 
as 
$$
begin
return query select * from employee;
end;
$$
language plpgsql;

postgres=# select * from f_get_employee();
 id |  name  | salary | departmentid 
----+--------+--------+--------------
  1 | kenyon |  30000 |            1
  2 | francs |  50000 |            1
  3 | digoal |  60000 |            2
  4 | narutu | 120000 |            3
(4 rows)

postgres=# select f_get_employee();
   f_get_employee    
---------------------
 (1,kenyon,30000,1)
 (2,francs,50000,1)
 (3,digoal,60000,2)
 (4,narutu,120000,3)
(4 rows)

postgres=# select * from f_get_employee() where id >3;
 id |  name  | salary | departmentid 
----+--------+--------+--------------
  4 | narutu | 120000 |            3
(1 row)

--新建的type在有些圖形化工具介面中可能看不到，
要查詢的話可以通過select * from pg_class where relkind='c'去查，c表示composite type

create type dept_salary as (departmentid int, totalsalary int);

create or replace function f_dept_salary() 
returns setof dept_salary 
as
$$
declare
rec dept_salary%rowtype;
begin
for rec in select departmentid, sum(salary) as totalsalary from f_get_employee() group by departmentid loop
  return next rec;
  end loop;
return;
end;
$$
language 'plpgsql';

create or replace function f_dept_salary_out(out o_dept text,out o_salary text) 
returns setof record as
$$
declare
    v_rec record;
begin
    for v_rec in select departmentid as dept_id, sum(salary) as total_salary from f_get_employee() group by departmentid loop
        o_dept:=v_rec.dept_id;
        o_salary:=v_rec.total_salary;  
        return next;
    end loop; 
end;
$$
language plpgsql;

postgres=# select * from f_dept_salary();
 departmentid | totalsalary 
--------------+-------------
            1 |       80000
            3 |      120000
            2 |       60000
(3 rows)

postgres=# select * from f_dept_salary_out();
 o_dept | o_salary 
--------+----------
 1      | 80000
 3      | 120000
 2      | 60000
(3 rows)

create or replace function f_get_rows(text) returns setof record as
$$
declare
rec record;
begin
for rec in EXECUTE 'select * from ' || $1 loop
return next rec;
end loop;
return;
end
$$
language 'plpgsql';

postgres=# select * from f_get_rows('department') as dept(deptid int, deptname text);
 deptid |  deptname  
--------+------------
      1 | Management
      2 | IT
      3 | BOSS
(3 rows)

postgres=# select * from f_get_rows('employee') as employee(employee_id int, employee_name text,employee_salary int,dept_id int);
 employee_id | employee_name | employee_salary | dept_id 
-------------+---------------+-----------------+---------
           1 | kenyon        |           30000 |       1
           2 | francs        |           50000 |       1
           3 | digoal        |           60000 |       2
           4 | narutu        |          120000 |       3
(4 rows)