POSTGRESQL- Query has no destination for result data - postgresql

Question

I'm new to postgres and to programming and I already searched for solution for this but I couldn't quite get it. I'm trying to make a function that will return information about all the customers on that particular country whenever I call the country. This is the error that pops up. I'm really sorry for asking this but I've been stuck here since yesterday.
ERROR: query has no destination for result data
HINT: If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT: PL/pgSQL function country(text) line 5 at SQL statement
Here is the function:
create or replace function country(text) returns text as $$
begin
select customer_id, customer.first_name, customer.last_name
from customer
inner join address on customer.address_id = address.address_id
inner join city on address.city_id = city.city_id
inner join country on city.country_id = country.country_id
where country = '$1';
end;
$$
language plpgsql;

Answer 1

If you are executing a select statement in a PL/pgSQL function, then you should place the result of the query in some variable(s) (= the destination). Then you work with the variable(s) in the function. You should also have a RETURN statement.
create or replace function country(text) returns text as $$
declare -- declare some variables
id integer;
fname text;
lname text;
begin
select customer_id, customer.first_name, customer.last_name
into id, fname, lname -- store query results in variables
from customer
inner join address on customer.address_id = address.address_id
inner join city on address.city_id = city.city_id
inner join country on city.country_id = country.country_id
where country = $1; -- don't quote parameter references
-- do something with the variables and return a value from the function
return format('%s: %s %s', id, upper(lname), fname);
end;
$$ language plpgsql;
Do note that the above only works if the query returns a single row. If the query returns multiple rows you can use a loop in the function. Even simpler, you can just return the results from the query like so:
create or replace function country(text)
returns table (id integer, first_name varchar, last_name varchar) as $$
begin
return query
select customer_id, customer.first_name, customer.last_name
from customer
inner join address on customer.address_id = address.address_id
inner join city on address.city_id = city.city_id
inner join country on city.country_id = country.country_id
where country = $1;
end;
$$ language plpgsql;
But like Evan Carroll said, unless you need a PL/pgSQL function to modify the data before returning it, you are better off with a simple view.

Answer 2

CREATE OR REPLACE FUNCTIOn func_process_client_contact(p_client_version_id bigint, p_publish_id bigint)
RETURNS TABLE(status_message character varying)
LANGUAGE plpgsql
AS $function$
declare
p_rowcount int;
BEGIN
-- validating input parameters : start
IF ( p_client_version_id IS NULL OR p_publish_id IS NULL )
THEN
RETURN;
END IF;
-- validating input parameters : end
WITH cte_target AS
(
SELECT
g.name AS clientname,
gcr.group_id AS clientid,
cr.id AS clientrelationid,
crc.id AS clientrelationcontactid,
crd.id AS clientrelationdesignation_id
FROM GROUPS g
JOIN group_client_relation gcr ON gcr.group_id =g.id
JOIN client_relation cr ON cr.id = gcr.client_relation_id
JOIN client_relation_contact crc ON crc.client_relation_id =cr.id
JOIN client_relation_designation crd ON cr.client_relation_designation_id =crd.id
)
SELECT * FROM cte_target ct WHERE ct.clientname='ABC';
GET DIAGNOSTICS p_rowcount = ROW_COUNT;
RAISE NOTICE 'returned % rows', p_rowcount;
IF ( p_rowcount=0 )
THEN
RETURN query SELECT 'hello' AS status_message;
ELSE
RETURN query SELECT 'Success' AS status_message;
END IF;
END
$function$

Answer 3

Please use below to get result of given function..
create or replace function country(in_parameter text,out out_res refcursor) as $$
begin
open out_res for
select customer_id, customer.first_name, customer.last_name
from customer
inner join address on customer.address_id = address.address_id
inner join city on address.city_id = city.city_id
inner join country on city.country_id = country.country_id
where country = '$1';
end;
$$
language plpgsql;

Answer 4

This is not normal for SQL. Normally, this would be a VIEW.
CREATE VIEW myView AS
SELECT customer_id, customer.first_name, customer.last_name
FROM customer
INNER JOIN address USING (address_id)
INNER JOIN city USING (city_id)
INNER JOIN country USING (country_id);
Then you do
SELECT * FROM myView WHERE country = ?
All of that said, if you insist on making this a function, and you shouldn't, you should make it a LANAGUAGE SQL and not LANGUAGE plppsql.

Answer 5

It worked for my colleague when she used OPEN MYCURS before the select query and RETURN MYCURS after the select query.

Answer 6

There might be some situations where we want to call another psql function from a function. If we just want to invoke the function and don't assign the return value to anything, then using select inner_function_call(); inside the main function will throw this error. As the hint suggests, use perform inner_function_call() instead.