Global temporary table example

Oracle Database Tips by Donald BurlesonMarch 3, 2015

Question: I need an example of how a global temporary table works. How does a global temporary table differs from a traditional temporary table or a WITH clause? I need a working example of a global temporary table. Do you need to drop the Global temporary table after each use?

Answer: When using a global temporary table you need only define the table once for the entire schema and then any user can insert directly into the table without the need to re-create the global temporary table.

drop table t1;
create table
t1
as
select sum(quantity) all_sales from stores;

Instead, a global temporary table does not required that the table be dropped and re-created and the global temporary tables are shared, such that each user gets a local copy of their rows, using the common definition.

create global temporary table
sum_quantity
(sum_qty number);

Once created, everyone shares the table definition and rows are private to each session. Here is an example of using a global temporary table:

SQL> insert into sum_quantity
2 (select sum(qty) from sales);

Note that the rows disappear after the SQL statement has completed, so that a GTT can be used over-and-over without redoing the table.

SQL> select * from sum_quantity;

SUM_QTY
----------
499

SQL> commit;

Commit complete.

SQL> select * from sum_quantity;

no rows selected

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