This process of extracting the elements of a collection is called collection unnesting.
refers to a LOB object attribute, then you must first initialize it with a value of empty or null. Also, if you are updating a LOB value using some method other than a direct to set the column to the value previously specified as the default value for the column.
The users can be named whatever you would like, however, these names are usually standardized: REPADMIN and REPPROXY.
In older databases, these names may be SNAPADMIN and SNAPPROXY.
SQL select * from emp_mv 2 order by deptno, job 3 / DEPTNO JOB ---------- --------- 10 MANAGER 10 PRESIDENT 10 SALES 20 ANALYST 20 CLERK 20 MANAGER 30 CLERK 30 MANAGER 30 SALESMAN 40 CLERK 40 DOGSBODY 12 rows selected.
The "on commit" means the materialized view will be refreshed whenever a change is committed in the master table.One-way MV technology allows a Materialized View to be refreshed in several ways (Figure 4.1) For systems with multiple master databases (such as global distributed Oracle systems), Updatable Materialized View replication can be integrated into a replication system that includes multiple master databases (Figure 4.4).As we discussed in Chapter 2, UMVs are a form of advanced replication.When used in the subquery of a DML statement, you can specify this clause in a subquery in the FROM clause but not in subquery in the can be a subquery, a column, a function, or a collection constructor.Regardless of its form, it must return a collection value—that is, a value whose type is nested table or varray.