Arrays in Oracle SQL

Question

Here's a simplified pseudo-code version of what I'd like to be able to do in PL-SQL (Oracle):

DECLARE
  mylist as ARRAY
BEGIN
  mylist (1) := '1'
  mylist (2) := '3'
  ...
  SELECT *
  FROM aTable
  WHERE aKey IN mylist;
END;

The SELECT should return the matching records for mylist(1), mylist(2) etc. It should be similar to ORing all the values, but of course we don't know in advance how many values we get.

How can I achieve this? I know that PL/SQL has some collection datatypes, but I can't seem to get them to work properly in SQL statements.

Thanks for any ideas.

Answer 1

This is easy to do with the TABLE() function. The one catch is that the array variable must use a type declared in SQL. This is because SELECT uses the SQL engine, so PL/SQL declarations are out of scope.

SQL> create or replace type numbers_nt as table of number
  2  /

Type created.

SQL>
SQL> declare
  2      l_array numbers_nt;
  3  begin
  4      l_array := numbers_nt (7521,7566,7654);
  5      for r in ( select ename
  6                 from emp
  7                 where empno in ( select *
  8                                  from table (l_array)
  9                                 )
 10               )
 11      loop
 12          dbms_output.put_line ( 'employee name = '||r.ename);
 13      end loop;
 14  end;
 15  /
employee name = PADFIELD
employee name = ROBERTSON
employee name = BILLINGTON

PL/SQL procedure successfully completed.

SQL>

Answer 2

A couple of suggestions:

1.) There's a CAST SQL keyword that you can do that might do the job... it makes your collection be treated as if it were a table.

2.) Pipelined functions. Basically a function returns data that looks like a table.

This link summarises the options and has a number of code listings that explain them.

http://www.databasejournal.com/features/oracle/article.php/3352091/CASTing-About-For-a-Solution-Using-CAST-and-Table-Functions-in-PLSQL.htm