What is key preserved table in oracle with example?

What is key preserved table in oracle with example?

A key-preserved table is a base table with a one-to-one row relationship with the rows in the view, via either the primary key or a unique key. In the example above, the cars table is a key-preserved table.

What is a key preserved view oracle?

Key preserved means the row from the base table will appear AT MOST ONCE in the output view on that table. For example, lets say I have tables T1 and T2 and a view: create view T.

What is key preserved?

Answer: In simple terms, a table is key preserved if the table key participates in the view as a key. In short, a key-preserved table has its key columns preserved through a SQL join.

Can we insert into view Oracle?

YES, you can Update and Insert into view and that edit will be reflected on the original table….

Can we update or delete records from the view?

Yes, possible to insert,update and delete to view. view is a virtual table. Same Perform as insert,update,delete query.. A view can be defined as a virtual table or a stored query and the data accessible through a view is not stored in the database as a distinct object.

Can we insert data into view?

We cannot insert or update data using view. The view is a virtual table. We can do those action, but it’s effect on real table data too. View is like a virtual table which enable us to get information of multiple tables.

When to use a key preserved table in Oracle?

If the view has the CHECK OPTION, join columns and columns taken from tables that are referenced more than once in the view must be shielded from UPDATE. For an INSERT statement, all columns into which values are inserted must come from a key-preserved table, and the view must not have the CHECK_OPTION.

What causes a deleted table to have a key preserved table?

In short, a key-preserved table has its key columns preserved through a SQL join. Also see the ORA-01752 error. Cause: The deleted table either had no key preserved tables, had more than one key-preserved table, or the key-preserved table was an unmerged view or a table from a read-only view.

Why is my join a non key table?

Both tables have primary keys defined and I thought that my join was uniquely identifying rows, but I’m still getting “ORA-01779: cannot modify a column which maps to a non key-preserved table”.

Do you need special treatment for key preserved tables?

If you want key preserved tables in a view, you must explicitly define the primary and foreign keys in the tables, or define unique indexes. The docs note that if you want a view to be inherently updatable, it must have special treatment for key preserved tables.