How do I write an SQL function that takes an unknown amount of numbers as parameters? - sql

Question

I am trying to write an Oracle SQL function that takes a list of numbers as arguments and return a pipelined list of table rows. My main problem is the quantity of numbers that can be passed is never certain with no real upper limit. I'll try and demonstrate what I mean:
Say I have a table defined as so:
create table items (
id number primary key,
class number,
data string
);
I want to return all rows that match one of a list of class numbers that I submit. The function I'm shooting at looks a little like this:
function get_list_items_from_class([unknown number of parameters]
in items.class%type)
return tbl_list_item pipelined; -- I have types defined to handle the return values
I've been looking at ways to handle defining a function that can take an undefined amount of integers and so far the most promising search has taken me to this page which explains about using collections and records. I don't think a VARRAY is what I'm looking for as the size has to be predefined. As Associative Array may be what I'm looking for, but before I spend a lot of time trying things out, I want to make sure the tool is fit for the job. I'm pretty inexperienced with Oracle SQL right now and I'm working on a time sensitive project.
Any help that you could offer would be appreciated. I realise that there are simpler ways to achieve what I'm trying to do in this example (simply multiple calls to a function that takes one parameter is one) but this example is simplified. Other parts of the project I'm working on require me to seek a solution using this multiple parameter method.
EDIT: That being said, I would welcome other design suggestions if I'm way off base with what I'm trying to attempt. It would be a learning experience if nothing else.
Many thanks in advance for your time.
EDIT: I will be accessing the database from proprietary client software written in Java.

Answer 1

You could use a table parameter as I linked in the comments or you could pass in a comma separated list of values parse it to a table and join to that.
something like this (with input_lst as a string):
select *
from tbl_list_item
where tbl_list_item.class in
(
select regexp_substr(input_lst,'[^,]+', 1, level) from dual
connect by regexp_substr(input_lst, '[^,]+', 1, level) is not null
);
adapted from https://blogs.oracle.com/aramamoo/entry/how_to_split_comma_separated_string_and_pass_to_in_clause_of_select_statement
Which choice is better depends on your expected number of entries and what is easier for your client side. I think with a small number (2-20) the comma separated is a fine choice. With a large number you probably want to pass a table.

Answer 2

A colleague actually suggested another way to achieve this and I think it is worth sharing. Basically, define a table type that can contain the arguments, then pass an array from the Java program that can be read from this table.
In my example, firstly define a table type of number:
create or replace type tbl_number as table of number;
Then, in the SQL package, define the function as:
function get_list_items_from_class(i_numbers in tbl_number)
return tbl_list_item pipelined;
The function in the package body has one major change (apart from the definition obviously). Use the following select statement:
select *
from tbl_list_item
where tbl_list_item.class in
(
select * from table(i_numbers)
);
This will select all the relevant items that match one of the integers that were passed to the "i_numbers" table. I like this way as it means less string parsing, both in the Java application and the SQL pacakage.
Here's how I passed the number arguments from the Java application using an ARRAY object.
ArrayDescriptor arrayDesc = ArrayDescriptor.createDescriptor("NUMBERS", con); //con is the database connection
ARRAY array = new ARRAY(arrayDesc, con, numberList.toArray()); // numberList is an ArrayList of integers which holds the arguments
array is then passed to the SQL function.