How to grant trigger access to a table - oracle

Question

I'm getting an error message for a trigger I've successfully created.
I've tried...
GRANT SELECT ON OTHER_TABLE TO [me];
call SYS.DBA_ASSIST.GRANT_OBJ_PERMS('dbo.MYTABLE','SELECT','dbo.OTHER_TABLE');`
Here is the code for the trigger...
CREATE OR REPLACE TRIGGER PREVENT_INVALID_ID
BEFORE INSERT OR UPDATE ON dbo.MYTABLE
FOR EACH ROW
DECLARE ROW_COUNT NUMBER;
BEGIN
SELECT COUNT(*) INTO ROW_COUNT
FROM [OTHER_TABLE] WHERE OTHER_TABLE_ID = :new.MYTABLE_ID;
IF ROW_COUNT = 0 THEN
RAISE_APPLICATION_ERROR(-20101, 'The ID provided is invalid.');
END IF;
END;`
The error message in user_errors says, "PL/SQL: ORA-00942: table or view does not exist"
Any idea how I can get the trigger to access OTHER_TABLE?
I understand that it is not possible to grant access/authorizations to triggers. But I'm unclear what code I need to run in order to allow the trigger to work.
Thanks in advance,
josh

Answer 1

If both MYTABLE and OTHER_TABLE belong to the same user, no privilege is required:
SQL> show user
USER is "SCOTT"
SQL> create table other_table (other_Table_id number);
Table created.
SQL> create table mytable (mytable_id number);
Table created.
SQL> create or replace trigger prevent_invalid_id
2 before insert or update on mytable
3 for each row
4 declare
5 row_count number;
6 begin
7 select count(*) into row_count
8 from other_table where other_table_id = :new.mytable_id;
9
10 if row_count = 0 then
11 raise_application_error(-20101, 'The ID provided is invalid');
12 end if;
13 end;
14 /
Trigger created.
SQL>
However, if they belong to different user, then OTHER_TABLE's owner has to grant SELECT privilege to me. Though, that's not enough - you have to either precede OTHER_TABLE with its owner name (e.g. other_user.other_table), or create a synonym in my own schema which points to other user's OTHER_TABLE. For example:
SQL> drop table other_table;
Table dropped.
SQL> connect mike/lion#xe
Connected.
SQL> create table other_table (other_Table_id number);
Table created.
SQL> grant select on other_table to scott;
Grant succeeded.
SQL> connect scott/tiger#xe
Connected.
SQL> create or replace trigger prevent_invalid_id
2 before insert or update on mytable
3 for each row
4 declare
5 row_count number;
6 begin
7 select count(*) into row_count
8 from MIKE.other_table where other_table_id = :new.mytable_id;
9
10 if row_count = 0 then
11 raise_application_error(-20101, 'The ID provided is invalid');
12 end if;
13 end;
14 /
Trigger created.
SQL>
Note line 8: MIKE.other_table.
Just to show what happens if you omit/remove owner's name:
SQL> l8
8* from MIKE.other_table where other_table_id = :new.mytable_id;
SQL> c/mike.//
8* from other_table where other_table_id = :new.mytable_id;
SQL> l
1 create or replace trigger prevent_invalid_id
2 before insert or update on mytable
3 for each row
4 declare
5 row_count number;
6 begin
7 select count(*) into row_count
8 from other_table where other_table_id = :new.mytable_id;
9
10 if row_count = 0 then
11 raise_application_error(-20101, 'The ID provided is invalid');
12 end if;
13* end;
SQL> /
Warning: Trigger created with compilation errors.
SQL> show err
Errors for TRIGGER PREVENT_INVALID_ID:
LINE/COL ERROR
-------- -----------------------------------------------------------------
4/3 PL/SQL: SQL Statement ignored
5/8 PL/SQL: ORA-00942: table or view does not exist
SQL>
See? ORA-00942.

Answer 2

Figured it out: GRANT SELECT ON OTHER_TABLE TO dbo
What threw me off is the use the words 'table owner' when I was looking for instructions on how to do this. I thought I was the table owner. Rather, it's the schema (dbo) that needs the privileges.