007 Postgres Command Line : psql : Create a function that returns a single value
As per the nature of recursion a function is a variable is a function.
Previously in 005 and 006 we wrote functions that returned subsets of queries they were effectively dynamic queries where I entered a parameter that was used in a select query. This effectively meant that although the function was returning a variable this was a query of a select statement.
What if we wish just to return a single value as in say translate centigrade to fahrenheit or some other calcuation.
In such case you simply state the function should return a variable and you state the variable type.
CREATE FUNCTION add(integer,integer) RETURNS integer
AS 'SELECT $1 + $2;'
RETURNS NULL ON NULL INPUT;
There are a few interesting things here which should be born in mind
In this case the addition is performed in SQL
I have to specifically name the language of the calculation (SQL) which suggests that if you stated another language it might accept it!
You still need to select the function to run it. This indicates that postgres 9.5 doesn’t executve functions as per some environments (ms access for example) – I have read that version 11 changed this and allows you to execute or perform a function. Ms Access you don’t even need to write execute simply the name of the function with the integers.
Variables are refererred to as to their input position unlike VBA where you dimension the variable and give it a name. I am unclear at the moment the advantages of the former or later but it is interesting nonetheless. I first came across something similar with autohotkey.
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