Oracle DB SQL Procedure Iterate over table with dynamic table bame - sql

Question

I'm working on an Oracle Stored procedure.
I need to iterate over rows of a table . I can do that using:
FOR eachrow IN table_name
LOOP
END LOOP;
But i need the table_name to be dynamic.
For example the table names are stored in some other table.
So, i can do FOR loop on that table and inside the loop ,i want to iterate through the rows of the new table.
Please suggest how i can achieve that.
Thanks,
Sash

Answer 1

This is not possible with a FOR eachrow IN table_name LOOP, you have to use a ref cursor instead:
First of all some sample data. These tables have some column names in common, in your inner for loop you can only access these columns, this is what I wrote in my comment above. Result type should be the same in the inner loop.
create table froc_a(id number, name varchar2(10), row_added date);
insert into froc_a values (1, '1', sysdate);
insert into froc_a values (2, '2', sysdate - 2);
insert into froc_a values (4, '4', sysdate - 4);
create table froc_b(id number, name2 varchar2(10), row_added date);
insert into froc_b values (1, 'b1', sysdate);
insert into froc_b values (2, 'b2', sysdate - 2);
insert into froc_b values (4, 'b4', sysdate - 4);
create table froc_c(id number, txt varchar2(10), row_added date);
insert into froc_c values (1, 'c1', sysdate);
insert into froc_c values (2, 'c2', sysdate - 2);
insert into froc_c values (4, 'c4', sysdate - 4);
Here is a first approach how to write it:
declare
TYPE curtype IS REF CURSOR;
l_cursor curtype;
l_param_id number;
l_id number;
l_val varchar2(100);
begin
l_param_id := 1;
-- Loop over your table names
for l_rec in (with tabnames(name) as
(select 'froc_a'
from dual
union all
select 'froc_b'
from dual
union all
select 'froc_c'
from dual)
select * from tabnames) loop
dbms_output.put_line(l_rec.name);
-- Open cursor for current table
open l_cursor for 'select id, row_added from ' || l_rec.name || ' where id = :1'
using l_param_id;
-- Loop over rows of current table
loop
fetch l_cursor
into l_id, l_val;
exit when l_cursor%notfound;
dbms_output.put_line(l_id || ', ' || l_val);
end loop;
end loop;
end;
Output:
froc_a
1, 06-APR-16
froc_b
1, 06-APR-16
froc_c
1, 06-APR-16