Updatable Materialized View with Union ALL

Question

(please don't ask about db structure)
DB: 11gR2
create table table_1  (
    id number primary key,
    val varchar2(100)
create table table_2  (
    id number primary key,
    val varchar2(100)
insert into table_1(id) values (0);
insert into table_1(id) values (2);
insert into table_1(id) values (3);
insert into table_1(id) values (4);
insert into table_1(id) values (5);
insert into table_2(id) values (10);
insert into table_2(id) values (12);
insert into table_2(id) values (13);
insert into table_2(id) values (14);
insert into table_2(id) values (15);
update table_1 set val='Table1 val:'||id;
update table_2 set val='Table2 val:'||id;
create view v_table_all as
select * from table_1
view V_TABLE_ALL created.
select * from v_table_all;
ID                     VAL                                                                                                 
0                      Table1 val:0                                                                                        
2                      Table1 val:2                                                                                        
3                      Table1 val:3                                                                                        
4                      Table1 val:4                                                                                        
5                      Table1 val:5                                                                                        
select column_name, updatable, insertable, deletable
from user_updatable_columns
where table_name = 'V_TABLE_ALL'
COLUMN_NAME                    UPDATABLE INSERTABLE DELETABLE
ID                             YES       YES        YES      
VAL                            YES       YES        YES      
update v_table_all set val='XXX changed' where id = 3;
1 row updated.
select * from table_1;
ID                     VAL                                                                                                 
0                      Table1 val:0                                                                                        
2                      Table1 val:2                                                                                        
3                      XXX changed                                                                                         
4                      Table1 val:4                                                                                        
5                      Table1 val:5                                                                                        
rollback;
select * from table_1;
ID                     VAL                                                                                                 
0                      Table1 val:0                                                                                        
2                      Table1 val:2                                                                                        
3                      Table1 val:3                                                                                        
4                      Table1 val:4                                                                                        
5                      Table1 val:5                                                                                        
create or replace view v_table_all as
select * from table_1
union select * from table_2;
view V_TABLE_ALL created.
select * from v_table_all;
ID                     VAL                                                                                                 
0                      Table1 val:0                                                                                        
2                      Table1 val:2                                                                                        
3                      Table1 val:3                                                                                        
4                      Table1 val:4                                                                                        
5                      Table1 val:5                                                                                        
10                     Table2 val:10                                                                                       
12                     Table2 val:12                                                                                       
13                     Table2 val:13                                                                                       
14                     Table2 val:14                                                                                       
15                     Table2 val:15  
select column_name, updatable, insertable, deletable
from user_updatable_columns
where table_name = 'V_TABLE_ALL'
COLUMN_NAME                    UPDATABLE INSERTABLE DELETABLE
ID                             NO        NO         NO       
VAL                            NO        NO         NO       
trying update:
update v_table_all set val='XXX changed' where id = 3;
SQL-Fehler: ORA-01732: Datenmanipulationsoperation auf dieser View nicht zulässig
01732. 00000 -  "data manipulation operation not legal on this view"
*Cause:   
*Action:
drop view v_table_all;
view V_TABLE_ALL dropped.all is ok before this point.
now we want create a new materialized view with some query
create  materialized view v_table_all
as
select * from table_1
union all select * from table_2 ;
materialized view V_TABLE_ALL created.
select column_name, updatable, insertable, deletable
from user_updatable_columns
where table_name = 'V_TABLE_ALL'
COLUMN_NAME                    UPDATABLE INSERTABLE DELETABLE
ID                             YES       YES        YES      
VAL                            YES       YES        YES       it seems to be ok with update.
but...
update v_table_all set val='XXX changed' where id = 3;
SQL-Fehler: ORA-01732: Datenmanipulationsoperation auf dieser View nicht zulässig
01732. 00000 -  "data manipulation operation not legal on this view"
*Cause:   
*Action:How can solve this issue??
Any suggestion

Answer 1

Looks like user_updatable_columns sort of thinks the MV is just a table - I don't know about that...
An MV on a single table can be updated - I tried that and it works:
create materialized view mv_table_1 for update
as
select * from table_1;I noticed [url http://download.oracle.com/docs/cd/E11882_01/server.112/e16579/advmv.htm#sthref294]examples stating the UNION ALL needs a "marker" so Oracle can know from the data which source table a row in the MV originates from - like this:
create materialized view v_table_all for update
as
select 'T1' tab_id, table_1.* from table_1
union all
select 'T2' tab_id, table_2.* from table_2 ;But that also fails (the "marker" requirement was specifically for FAST REFRESH, so it was just a long shot ;-) )
What are you planning to do?
<li>Create the MV.
<li>Update records in the MV - which then is no longer consistent with the source data.
<li>Schedule a complete refresh once in a while - thereby overwriting/losing the updates in the MV.
If that is the case, I suggest using a true table rather than an MV.
<li>Create table t_table_all as select ... .
<li>Update records in the table - which then is no longer consistent with the source data.
<li>Schedule a job to delete table and insert into table select ... once in a while - thereby overwriting/losing the updates in the table.
In other words a kind of "do it yourself MV".
I cannot see another way at the moment? But perhaps try in the data warehousing forum - the people there may have greater experience with MV's ;-)