How to dynamically construct table name - sql

Question

I would like to construct a query where a table name is based off of another table's column mod 12. For example:
SELECT *
FROM table_b_XX
where XX here is determined by table_a.column_a % 12.

Answer 1

Presuming you have such a tables:
SQL> create table table_a as
2 select 1212 as column_a from dual;
Table created.
As the following result returns 0, we need table_b_00 so I'll create it:
SQL> select mod(1212, 12) from dual;
MOD(1212,12)
------------
0
SQL> create table table_b_00 as select 'table 00' name from dual;
Table created.
SQL> create table table_b_01 as select 'table 01' name from dual;
Table created.
Now, create a function which returns ref cursor; it selects rows from a table whose name is designed by the help of the table_a contents:
SQL> create or replace function f_test return sys_refcursor
2 is
3 l_str varchar2(200);
4 rc sys_refcursor;
5 begin
6 select 'select * from table_b_' || lpad(mod(a.column_a, 12), 2, '0')
7 into l_str
8 from table_a a;
9
10 open rc for l_str;
11 return rc;
12 end f_test;
13 /
Function created.
Let's try it:
SQL> select f_test from dual;
F_TEST
--------------------
CURSOR STATEMENT : 1
CURSOR STATEMENT : 1
NAME
--------
table 00
Right; that's contents of table_b_00.

Answer 2

Consider the following meta code:
DECLARE
n VARCHAR2(32767);
r VARCHAR2(32767);
BEGIN
SELECT column_a INTO name FROM table_a;
EXECUTE IMMEDIATE 'SELECT r FROM table_b_'||n INTO r;
END;
/