Calling PL/SQL functions in SQL

Question

Hi,
I had a question on the behaviour of PL/SQL function when they are embedded in SQL queries.
I have simple PL/SQl function:
function get_city_id
(vCUSTOMER_GROUP_ID IN NUMBER)
RETURN VARCHAR2 AS
vIDs VARCHAR2(1000);
begin
vIDs := '2,3';
RETURN vIDs;
end;
I use an SQL query call this PL SQL function;
select equipment_id from equipment where equipment_type_id in (get_city_id(0));
When I run this query I get this error:
ERROR at line 1:
ORA-01722: invalid number
I understand that the SQL compiler is complaining that get_city_id() function is not returning a number. but isn't the PL/SQL suppose to be replace with whatever string is returned from the function.
This brings me to the second question: How can we return multiple values from a function to the SQL query, when the function is called in a SQL query. In my above explame, can the get_city_id() function return more than one city id and if yes, the how?
Thanks for the help in advance
regards
Alankar

Answer 1

How can we return multiple values from a function to the SQL query,Have it return a collection, e.g.
CREATE OR REPLACE TYPE VARCHAR2_TT AS TABLE OF VARCHAR2(4000)
CREATE OR REPLACE FUNCTION test_collection
    RETURN VARCHAR2_TT
AS
BEGIN
    RETURN VARCHAR2_TT(1,2,3);
END;
SELECT *
FROM   employees
WHERE  emp_id IN
       ( SELECT column_value
         FROM   TABLE(test_collection) );