What is GLOBAL TEMPORARY TABLE and It's significance ?

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What is GLOBAL TEMPORARY TABLE and It's significance ?..

Answer / pradeep

Creation of Global Temporary Tables
The data in a global temporary table is private, such that
data inserted by a session can only be accessed by that
session. The session-specific rows in a global temporary
table can be preserved for the whole session, or just for
the current transaction. The ON COMMIT DELETE ROWS clause
indicates that the data should be deleted at the end of the
transaction.

CREATE GLOBAL TEMPORARY TABLE my_temp_table (
column1 NUMBER,
column2 NUMBER
) ON COMMIT DELETE ROWS;

In contrast, the ON COMMIT PRESERVE ROWS clause indicates
that rows should be preserved until the end of the session.

CREATE GLOBAL TEMPORARY TABLE my_temp_table (
column1 NUMBER,
column2 NUMBER
) ON COMMIT PRESERVE ROWS;

Miscellaneous Features

* If the TRUNCATE statement is issued against a
temporary table, only the session specific data is trucated.
There is no affect on the data of other sessions.
* Data in temporary tables is automatically delete at
the end of the database session, even if it ends abnormally.
* Indexes can be created on temporary tables. The
content of the index and the scope of the index is that same
as the database session.
* Views can be created against temporary tables and
combinations of temporary and permanent tables.
* Temporary tables can have triggers associated with them.
* Export and Import utilities can be used to transfer
the table definitions, but no data rows are processed.
* There are a number of restrictions related to
temporary tables but these are version specific.