Functions
Create a new function
$$
CREATE FUNCTION add(integer, integer) RETURNS integer
AS 'select $1 + $2;'
LANGUAGE SQL
IMMUTABLE
RETURNS NULL ON NULL INPUT;
$$// Create a function to add 2 integers (SQL)
This function takes two integers as parameters
IMMUTABLE means that the function cannot modify the database and always returns the same result when given the same argument values.
Calling function
select add(5,9);
add
-----
14
(1 row)// Function call (SQL)
List functions
\df
List of functions
Schema | Name | Result data type | Argument data types | Type
--------+------+------------------+---------------------+--------
public | add | integer | integer, integer | normal
(1 row)// Display all Functions (psql)
\df+
// Display all functions and additional information, including owner, source code, and description, etc. (psql)
Edit function
\ef myfunction
// Edit a function in default editor (psql)