using comma separated values inside IN clause for NUMBER column

Question

I have 2 procedures inside a package. I am calling one procedure to get a comma separated list of user ids.

I am storing the result in a VARCHAR variab

Answer 1

Do you really need to return a comma-separated list? It would generally be much better to declare a collection type

CREATE TYPE num_table
    AS TABLE OF NUMBER;

Declare a function that returns an instance of this collection

CREATE OR REPLACE FUNCTION get_nums
  RETURN num_table
IS
  l_nums num_table := num_table();
BEGIN
  for i in 1 .. 10
  loop
    l_nums.extend;
    l_nums(i) := i*2;
  end loop;
END;

and then use that collection in your query

SELECT *
  FROM users_table
 WHERE user_id IN (SELECT * FROM TABLE( l_nums ));

It is possible to use dynamic SQL as well (which @Sebas demonstrates). The downside to that, however, is that every call to the procedure will generate a new SQL statement that needs to be parsed again before it is executed. It also puts pressure on the library cache which can cause Oracle to purge lots of other reusable SQL statements which can create lots of other performance problems.