PostgreSQL/Store Procedure Function/Function Parameter
Содержание
- 1 "Anyelement" parameter
- 2 Here the $1 references the value of the first function argument whenever the function is invoked
- 3 OUT parameter
- 4 Output parameters are most useful when returning multiple values
- 5 Pass constant to function
- 6 Pass in a whole row
- 7 Real number parameter
- 8 Two out parameters
- 9 Use defined data type as the 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=#
</source>
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=#
</source>
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>