PostgreSQL/Store Procedure Function/Function Parameter

"Anyelement" parameter

postgres=#
postgres=# CREATE FUNCTION is_greater(anyelement, anyelement) RETURNS boolean AS $$
postgres$#    SELECT $1 > $2;
postgres$# $$ LANGUAGE SQL;
CREATE FUNCTION
postgres=#
postgres=# SELECT is_greater(1, 2);
   REATE
 is_greater
------------
 f
(1 row)
postgres=#
postgres=# drop function is_greater(anyelement, anyelement);
DROP FUNCTION
postgres=#
postgres=#

Here the $1 references the value of the first function argument whenever the function is invoked

postgres=#
postgres=# CREATE TABLE employee (
postgres(#     ID         int,
postgres(#     name       varchar(10),
postgres(#     salary     real,
postgres(#     start_date date,
postgres(#     city       varchar(10),
postgres(#     region     char(1)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (1,  "Jason", 40420,  "02/01/94", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (4,  "Linda", 40620,  "11/04/97", "New York", "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (5,  "David", 80026,  "10/05/98", "Vancouver","W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (7,  "Alison",90620,  "08/07/00", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W");
INSERT 0 1
postgres=#
postgres=# select * from employee;
 id |  name  | salary | start_date |   city    | region
----+--------+--------+------------+-----------+--------
  1 | Jason  |  40420 | 1994-02-01 | New York  | W
  2 | Robert |  14420 | 1995-01-02 | Vancouver | N
  3 | Celia  |  24020 | 1996-12-03 | Toronto   | W
  4 | Linda  |  40620 | 1997-11-04 | New York  | N
  5 | David  |  80026 | 1998-10-05 | Vancouver | W
  6 | James  |  70060 | 1999-09-06 | Toronto   | N
  7 | Alison |  90620 | 2000-08-07 | New York  | W
  8 | Chris  |  26020 | 2001-07-08 | Vancouver | N
  9 | Mary   |  60020 | 2002-06-09 | Toronto   | W
(9 rows)
postgres=#
postgres=#
postgres=# CREATE FUNCTION myFunction(text) RETURNS employee
postgres-#    AS $$ SELECT * FROM employee WHERE name = $1 $$
postgres-#    LANGUAGE SQL;
CREATE FUNCTION
postgres=#
postgres=# -- Here the $1 references the value of the first function argument whenever the function is invoked.
postgres=#
postgres=#
postgres=# select * from myFunction("James");
 id | name  | salary | start_date |  city   | region
----+-------+--------+------------+---------+--------
  6 | James |  70060 | 1999-09-06 | Toronto | N
(1 row)
postgres=#
postgres=#
postgres=# drop function myFunction(text);
DROP FUNCTION
postgres=# drop table employee;
DROP TABLE
postgres=#
postgres=#

OUT parameter

postgres=#
postgres=#
postgres=# CREATE FUNCTION sales_tax(subtotal real, OUT tax real) AS $$
postgres$# BEGIN
postgres$#    tax := subtotal * 0.06;
postgres$# END;
postgres$# $$ LANGUAGE plpgsql;
postgres=#
postgres=# select sales_tax(100);
   REATE
 sales_tax
-----------
         6
(1 row)
postgres=#
postgres=# drop function sales_tax(subtotal real, OUT tax real);
DROP FUNCTION
postgres=#
postgres=#

Output parameters are most useful when returning multiple values

postgres=#
postgres=# -- Output parameters are most useful when returning multiple values
postgres=#
postgres=# CREATE FUNCTION sum_n_product(x int, y int, OUT sum int, OUT prod int) AS $$
postgres$# BEGIN
postgres$#    sum := x + y;
postgres$#    prod := x * y;
postgres$# END;
postgres$# $$ LANGUAGE plpgsql;
CREATE FUNCTION
postgres=#
postgres=# select sum_n_product(1,2);
     REATE
 sum_n_product
---------------
 (3,2)
(1 row)
postgres=#
postgres=# drop function sum_n_product(x int, y int, OUT sum int, OUT prod int);
DROP FUNCTION
postgres=#
postgres=#

Pass constant to function

postgres=#
postgres=# CREATE FUNCTION "you_me" (integer) RETURNS integer AS "
postgres"#   DECLARE
postgres"#    RENAME $1 TO user_no;
postgres"#     --you INTEGER := 5;
postgres"#   BEGIN
postgres"#     return user_no;
postgres"#   END;" LANGUAGE "plpgsql";
CREATE FUNCTION
postgres=#
postgres=# select you_me(1);
 you_me
--------
      1
(1 row)
postgres=#

Pass in a whole row

postgres=#
postgres=# CREATE TABLE employee (
postgres(#     ID         int,
postgres(#     name       varchar(10),
postgres(#     salary     real,
postgres(#     start_date date,
postgres(#     city       varchar(10),
postgres(#     region     char(1)
postgres(# );
CREATE TABLE
postgres=#
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (1,  "Jason", 40420,  "02/01/94", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (4,  "Linda", 40620,  "11/04/97", "New York", "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (5,  "David", 80026,  "10/05/98", "Vancouver","W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (7,  "Alison",90620,  "08/07/00", "New York", "W");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N");
INSERT 0 1
postgres=# insert into employee (ID, name,    salary, start_date, city,       region)
postgres-#               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W");
INSERT 0 1
postgres=#
postgres=# select * from employee;
                         REATE
 id |  name  | salary | start_date |   city    | region
----+--------+--------+------------+-----------+--------
  1 | Jason  |  40420 | 1994-02-01 | New York  | W
  2 | Robert |  14420 | 1995-01-02 | Vancouver | N
  3 | Celia  |  24020 | 1996-12-03 | Toronto   | W
  4 | Linda  |  40620 | 1997-11-04 | New York  | N
  5 | David  |  80026 | 1998-10-05 | Vancouver | W
  6 | James  |  70060 | 1999-09-06 | Toronto   | N
  7 | Alison |  90620 | 2000-08-07 | New York  | W
  8 | Chris  |  26020 | 2001-07-08 | Vancouver | N
  9 | Mary   |  60020 | 2002-06-09 | Toronto   | W
(9 rows)
postgres=#
postgres=#
postgres=# CREATE FUNCTION concat_selected_fields(in_t employee) RETURNS text AS $$
postgres$# BEGIN
postgres$#    RETURN in_t.ID || in_t.name || in_t.city || in_t.region;
postgres$# END;
postgres$# $$ LANGUAGE plpgsql;
CREATE FUNCTION
postgres=#
postgres=# select concat_selected_fields(employee.*) from employee;
         REATE
 concat_selected_fields
------------------------
 1JasonNew YorkW
 2RobertVancouverN
 3CeliaTorontoW
 4LindaNew YorkN
 5DavidVancouverW
 6JamesTorontoN
 7AlisonNew YorkW
 8ChrisVancouverN
 9MaryTorontoW
(9 rows)
postgres=#
postgres=#
postgres=# drop function concat_selected_fields(in_t employee);
DROP FUNCTION
postgres=# drop table employee;
DROP TABLE
postgres=#
postgres=#

Real number parameter

postgres=#
postgres=#
postgres=#
postgres=# CREATE FUNCTION sales_tax(subtotal real) RETURNS real AS $$
postgres$# BEGIN
postgres$#    RETURN subtotal * 0.06;
postgres$# END;
postgres$# $$ LANGUAGE plpgsql;
postgres=#
postgres=#
postgres=# select sales_tax(100);
   REATE
 sales_tax
-----------
         6
(1 row)
postgres=#
postgres=# drop function sales_tax( real);
DROP FUNCTION
postgres=#
postgres=#

Two out parameters

postgres=#
postgres=# CREATE FUNCTION dup (f1 anyelement, OUT f2 anyelement, OUT f3 anyarray)
postgres-# AS "select $1, array[$1,$1]" LANGUAGE sql;
CREATE FUNCTION
postgres=#
postgres=# SELECT * FROM dup(22);
    REATE
 f2 |   f3
----+---------
 22 | {22,22}
(1 row)
postgres=#
postgres=# drop function dup(f1 anyelement, OUT f2 anyelement, OUT f3 anyarray);
postgres=#
postgres=#

Use defined data type as the function parameter

postgres=#
postgres=# CREATE TYPE inventory_item AS (
postgres(#    name            text,
postgres(#    supplier_id     integer,
postgres(#    price           numeric
postgres(# );
CREATE TYPE
postgres=#
postgres=# CREATE TABLE on_hand (
postgres(#    item      inventory_item,
postgres(#    count     integer
postgres(# );
CREATE TABLE
postgres=#
postgres=# INSERT INTO on_hand VALUES (ROW("fuzzy dice", 42, 1.99), 1000);
INSERT 0 1
postgres=#
postgres=# select * from on_hand;
          item          | count
------------------------+-------
 ("fuzzy dice",42,1.99) |  1000
(1 row)
postgres=#
postgres=#
postgres=# CREATE FUNCTION price_extension(inventory_item, integer) RETURNS numeric
postgres-# AS "SELECT $1.price * $2" LANGUAGE SQL;
CREATE FUNCTION
postgres=#
postgres=# select price_extension(ROW("fuzzy dice", 42, 1.99), 1000);
 price_extension
-----------------
         1990.00
(1 row)
postgres=#
postgres=# drop function price_extension(inventory_item, integer);
DROP FUNCTION
postgres=# drop table on_hand;
DROP TABLE
postgres=# drop type inventory_item;
DROP TYPE
postgres=#
postgres=#