The clause preallocates a set of sequence numbers and keeps them in memory so that sequence numbers can be accessed faster.

When the last of the sequence numbers in the cache has been used, the database reads another set of numbers into the cache.

updating synonym-16

Note: It is not necessary that the key or keys of a table be selected for it to be key preserved.

It is sufficient that if the key or keys were selected, then they would also be keys of the result of the join.

You can use views in almost the same way as tables.

You can query, update, insert into, and delete from views, just as you can standard tables.

In this case, the view is considered "created with errors." For example, when a view is created that refers to a nonexistent table or an invalid column of an existing table, or when the view owner does not have the required privileges, the view can be created anyway and entered into the data dictionary. To create a view with errors, you must include the .

When you try to create such a view, the database returns a message indicating the view was created with errors.

If developers have such constructs in applications, then you should encourage the developers to replace them with access to sequences.

Sequences eliminate serialization and improve the concurrency of an application.

SELECT COLUMN_NAME, UPDATABLE FROM USER_UPDATABLE_COLUMNS WHERE TABLE_NAME = 'EMP_DEPT'; COLUMN_NAME UPD ------------------------------ --- EMPNO YES ENAME YES DEPTNO YES SAL YES DNAME NO LOC NO 6 rows selected.

statement lets you locate recompilation errors before run time.

If conditions later change so that the query of an invalid view can be executed, the view can be recompiled and be made valid (usable).