PL/SQL Select and Update statement inside OPEN - FOR - oracle

Question

So I have a pl/sql function and I want to select and update table inside open for statement
It looks like this:
table_a
id | status | document_id |
create or replace function a(p_document_id in number)
return sys_refcursor
is
result sys_refcursor;
begin
open result for
select id
from table_a t
where t.document_id = p_document_id;
update table_a t
set t.status = 1
where id in (select id
from table_a t
where t.document_id = p_document_id);
return result;
end;
/
But it is not working. Is there some method to do this? thanks in advance

Answer 1

This is a sample table:
SQL> select * from table_a;
ID DOCUMENT_ID STATUS
---------- ----------- ----------
1 100 0
Function you wrote compiles, but doesn't work because functions - normally - don't do DML:
SQL> select a(100) from dual;
select a(100) from dual
*
ERROR at line 1:
ORA-14551: cannot perform a DML operation inside a query
ORA-06512: at "SCOTT.A", line 11
SQL>
It, though, would work from PL/SQL, e.g.
SQL> declare
2 l_rc sys_refcursor;
3 begin
4 l_rc := a(100);
5 end;
6 /
PL/SQL procedure successfully completed.
SQL> select * from table_a;
ID DOCUMENT_ID STATUS
---------- ----------- ----------
1 100 1
SQL>
But, if you want to be able to call the function from PL/SQL, it has to be an autonomous transaction, which also means that you have to commit within:
SQL> rollback;
Rollback complete.
SQL> create or replace function a(p_document_id in number)
2 return sys_refcursor
3 is
4 result sys_refcursor;
5 pragma autonomous_transaction; --> this
6 begin
7 open result for
8 select id
9 from table_a t
10 where t.document_id = p_document_id;
11
12 update table_a t
13 set t.status = 1
14 where id in (select id
15 from table_a t
16 where t.document_id = p_document_id);
17
18 commit; --> this
19
20 return result;
21 end;
22 /
Function created.
Let's try it:
SQL> select a(100) from dual;
A(100)
--------------------
CURSOR STATEMENT : 1
CURSOR STATEMENT : 1
ID
----------
1
SQL> select * from table_a;
ID DOCUMENT_ID STATUS
---------- ----------- ----------
1 100 1
SQL>
This might, or might not be OK. Autonomous transactions can be tricky and we usually use them for logging purposes, so that their commit doesn't affect the main transaction.