How do you create a temporary table in an Oracle database?
Defining a temporary table in Oracle is as easy as using CREATE GLOBAL TEMPORARY TABLE:
Data in temp_table_name follows the "live fast, die young" concept: it doesn't survive beyond the transaction. For data to survive the brutal harshness of end-of-session winters, use ON COMMIT PRESERVE ROWS instead.
Nuts and bolts of Oracle's temporary tables
Working with temporary tables effectively in Oracle requires more than just creating them. Let's get into good habits, quirks, and advanced applications of these temperamental entities.
Matching problem to table type
Global Temporary Table or Private Temporary Table? Knowing your needs can prevent unnecessary heartbreak:
- Global Temporary Table: Perfect for when you need data to persist across multiple transactions within one session.
- Private Temporary Table (
From the world of Oracle 18c): Tailored for brief, in-memory operations enclosed within one transaction or session.
Optimizing temporary table usage
Avoid the hit-and-run method of dynamically creating and dropping temporary tables. In the world of Oracle, that's not cool. It's better to define the table structure once that would then do its 'now you see me, now you don't' act for each session.
Harnessing the power of inline views and Materialized CTEs
Embark on a pursuit for better performance by replacing temporary tables with inline views or materialized Common Table Expressions (CTEs). The /+ MATERIALIZE/+ hint plays the 'invisible man': storing the result, like a temporary table, but actually not existing. Spooky, isn't it!
One ring to rule them all
Instead of creating disparate SQL operations, why not wield the "one ring" of SQL statements which rules them all. You'll have less need for temporary tables, and you’ll be closer to being the SQL Lord.
Understanding permissions and restrictions
Some may consider it an "unfair game", but not all users with CREATE TABLE privileges can create temporary tables. These muggles (ordinary users or report writers without wizardry powers) need alternate spells like subqueries or views.
Mastering the Oracle's magic
Oracle's vast armory includes some powerful spells (aka features) that can reduce your reliance on temporary tables. Get friendly with the subquery factoring (the WITH clause) or the window functions - they can turn complex queries into a piece of cake.
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