How to declare variable and assign value into that in postgresql?

Question

I'm very new in postgresql. I read many posts in this questions, but still don't get correct answer in my simple problem and keep receiving syntax error. I'm trying declare new string variable named parents_d and in the following lines trying to assign new value as well. Please help me!

CREATE OR REPLACE FUNCTION retrieve_parents(cid integer) RETURNS text AS $$ 
BEGIN
    DECLARE pd text;    
    pd:= 'function';
    RETURN concat(cid,pd);
END;
$$ LANGUAGE plpgsql;

ERROR: duplicate declaration at or near "pd" LINE 4: pd:= 'function'; ^

********** Error **********

ERROR: duplicate declaration at or near "pd" SQL state: 42601 Character: 104

Answer 1

try like this

SQL Fiddle Demo

CREATE FUNCTION retrieve_parents(cid integer) RETURNS text AS $$
DECLARE pd text;    
BEGIN

    pd:= 'function';
    RETURN concat(cid,pd);

END; $$
LANGUAGE PLPGSQL