PL/SQL create view base on dynamic table name - oracle

Question

I'm trying to create a view that access all the tables starting with the same name, they have the exactly same structure, and in time there will be more.
Table Names:
TEMP_ENTITIES_1000
TEMP_ENTITIES_1001
TEMP_ENTITIES_1002
and in the future there will be
TEMP_ENTITIES_1003
TEMP_ENTITIES_1004
and so on...
What I need is to use list of tables from the following script and then use the result the list of object name result to access in a view.
select object_name
from user_objects
where object_type = 'TABLE'
and object_name like upper('temp_entities_%');
create view entities_join as
select * from (object_name)
Is it possible to achieve?

Answer 1

In modern versions of Oracle you may use SQL table macros without scheduled anything. It will build dynamic query on-the-fly and may be used as a plain view.
Below is the example:
SQL> insert all
2 when mod(rownum, 5) = 0 then into TEMP_ENTITIES_1000 values (l, dt, val)
3 when mod(rownum, 5) = 1 then into TEMP_ENTITIES_1001 values (l, dt, val)
4 when mod(rownum, 5) = 2 then into TEMP_ENTITIES_1002 values (l, dt, val)
5 when mod(rownum, 5) = 3 then into TEMP_ENTITIES_1003 values (l, dt, val)
6 when mod(rownum, 5) = 4 then into TEMP_ENTITIES_1004 values (l, dt, val)
7
8 select
9 level as l,
10 sysdate + level as dt,
11 level as val
12 from dual
13 connect by level < 10;
9 rows inserted.
SQL>
SQL> create or replace function f_temp_entities_union
2 /*Create a macro*/
3 return varchar2 SQL_MACRO
4 is
5 v_union varchar2(4000);
6 begin
7 select listagg('select ''' || table_name || ''' as src, a.* from ' || table_name || ' a ', chr(10) || 'union all' || chr(10))
8 into v_union
9 from all_tables
10 where table_name like 'TEMP_ENTITIES%'
11 and owner = sys_context('USERENV', 'CURRENT_SCHEMA')
12 ;
13
14 return v_union;
15 end;
16 /
Function F_TEMP_ENTITIES_UNION compiled
SQL>
SQL> select *
2 from f_temp_entities_union();
TEMP_ENTITIES_1000 5 20.09.21 5
TEMP_ENTITIES_1001 1 16.09.21 1
TEMP_ENTITIES_1001 6 21.09.21 6
TEMP_ENTITIES_1002 2 17.09.21 2
TEMP_ENTITIES_1002 7 22.09.21 7
TEMP_ENTITIES_1003 3 18.09.21 3
TEMP_ENTITIES_1003 8 23.09.21 8
TEMP_ENTITIES_1004 4 19.09.21 4
TEMP_ENTITIES_1004 9 24.09.21 9
9 rows selected.
SQL>
SQL> /*Add new table*/
SQL> create table TEMP_ENTITIES_1005 as select * from TEMP_ENTITIES_1001 where 1 = 0;
Table TEMP_ENTITIES_1005 created.
SQL> insert into TEMP_ENTITIES_1005
2 select 1000 + rownum, sysdate + rownum, rownum - 100 from TEMP_ENTITIES_1000;
1 row inserted.
SQL>
SQL> /*Check that new data is here*/
SQL> select *
2 from v_demo;
TEMP_ENTITIES_1000 5 20.09.21 5
TEMP_ENTITIES_1001 1 16.09.21 1
TEMP_ENTITIES_1001 6 21.09.21 6
TEMP_ENTITIES_1002 2 17.09.21 2
TEMP_ENTITIES_1002 7 22.09.21 7
TEMP_ENTITIES_1003 3 18.09.21 3
TEMP_ENTITIES_1003 8 23.09.21 8
TEMP_ENTITIES_1004 4 19.09.21 4
TEMP_ENTITIES_1004 9 24.09.21 9
TEMP_ENTITIES_1005 1001 16.09.21 -99
10 rows selected.

Answer 2

Is it possible? Yes, using dynamic SQL.
However, from what you described, it looks that data model you use is wrong. You should have only one table with identifier that makes the difference (those 1000, 1001, ... values).
Then you wouldn't need a view at all, and do everything with that single table. I suggest you consider doing so.
Here's an example of what you might do (the way you asked):
Several sample tables:
SQL> select * from temp_entities_1000;
ID NAME
---------- ------
1000 Little
SQL> select * from temp_entities_1001;
ID NAME
---------- ----
1001 Foot
SQL> select * from temp_entities_1002;
ID NAME
---------- -----
1002 Scott
Procedure:
SQL> DECLARE
2 l_str VARCHAR2 (2000);
3 BEGIN
4 FOR cur_r IN (SELECT object_name
5 FROM user_objects
6 WHERE object_type = 'TABLE'
7 AND object_name LIKE 'TEMP_ENTITIES%')
8 LOOP
9 l_str :=
10 l_str || ' select * from ' || cur_r.object_name || ' union all ';
11 END LOOP;
12
13 l_str :=
14 'create or replace view entities_join as '
15 || RTRIM (l_str, ' union all');
16
17 EXECUTE IMMEDIATE l_str;
18 END;
19 /
PL/SQL procedure successfully completed.
Result:
SQL> select * from entities_join;
ID NAME
---------- ------
1000 Little
1001 Foot
1002 Scott
SQL>
You'd have to run that procedure every time new table is created so that it is included into the view.