Oracle - Anonymous Procedure to loop through multiple tables (dynamically) - Query returning multiple rows

Question

I need to fire the same query on multiple tables. Query might return zero, one or more number of rows.

I can loop through the tables using EXECUTE IMMEDIATE but for returning multiple rows I would need a datatype so I think I would need to keep it as CURSOR.

for ease, lets say I need to execute below query on 2 tables - table1 and table2

Table1 has following columns

datetime
device_name
value1
value2

Table2 has following columns

datetime
device_name
value3
value4

Query to be executed on both the tables as below:

select datetime, count(*) from table_name group by datetime;

Whats the best approach here?

please note that I can't create any DB objects (proc/function). Has to be anonymous block only.

Answer 1

As long as the cursor structures are the same, you can loop through with some dynamic ref cursors, eg

SQL> set serverout on
SQL> declare
  2    tablist sys.odcivarchar2list :=
  3      sys.odcivarchar2list('ALL_OBJECTS','USER_OBJECTS');
  4    rc sys_refcursor;
  5
  6    date_results sys.odcidatelist := sys.odcidatelist();
  7    count_results sys.odcinumberlist := sys.odcinumberlist();
  8  begin
  9    for i in 1 .. tablist.count
 10    loop
 11      open rc for
 12        replace(q'{select trunc(created,'YYYY'), count(*) from @@@ group by trunc(created,'YYYY') order by 1}', '@@@',tablist(i));
 13      fetch rc bulk collect into date_results, count_results;
 14      close rc;
 15
 16      dbms_output.put_line(tablist(i));
 17      for c in 1 .. date_results.count
 18      loop
 19        dbms_output.put_line(rpad(date_results(c),20)||lpad(count_results(c),20));
 20      end loop;
 21    end loop;
 22  end;
 23  /
ALL_OBJECTS
01-JAN-17                          67892
01-JAN-18                           6228
USER_OBJECTS
01-JAN-18                           1093

PL/SQL procedure successfully completed.