PostgreSQL/Store Procedure Function/Function Parameter

"Anyelement" parameter

   <source lang="sql">

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=#

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

   <source lang="sql">

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=#

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OUT parameter

   <source lang="sql">

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=#

      </source>
   
  

Output parameters are most useful when returning multiple values

   <source lang="sql">

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=#

      </source>
   
  

Pass constant to function

   <source lang="sql">

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=#

      </source>
   
  

Pass in a whole row

   <source lang="sql">

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=#

      </source>
   
  

Real number parameter

   <source lang="sql">

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=#

      </source>
   
  

Two out parameters

   <source lang="sql">

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=#

      </source>
   
  

Use defined data type as the function parameter

   <source lang="sql">

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=#

      </source>