Introduction to TEMP Tables

Introduction

Temporary tables (TEMP tables) are a special type of table that exists only for the duration of your database session. They provide a workspace for intermediate calculations without cluttering your database with permanent objects.

In this tutorial, you will learn:

What temporary tables are and how they differ from regular tables
When to use temporary tables
The lifecycle of temporary tables
Key benefits and limitations

What is a Temporary Table?

Session-Scoped Storage

A temporary table is a table that:

Is created within a database session
Is automatically deleted when the session ends
Is visible only to your session (in most databases)
Behaves like a regular table while it exists

Diagram showing temporary table lifecycle: creation within a session, usage, and automatic deletion when session ends

Regular Tables vs TEMP Tables

Key Differences

Comparison Table

Feature	Regular Table	TEMP Table
Lifespan	Until explicitly dropped	Session only
Visibility	All users	Current session only
Storage	Disk (permanent)	Memory or temp disk
Logging	Full transaction logging	Minimal
Backup	Included in backups	Not backed up
Cleanup	Manual DROP required	Automatic
Namespace	Schema namespace	Session namespace
Indexes	Yes	Yes (session-scoped)
Use case	Permanent data	Intermediate work

Why Use Temporary Tables?

Benefits of Temporary Tables

Types of Temporary Tables

Database-Specific Variations

Database Syntax Overview

Database	Local Temp Table	Global Temp Table
SQLite	`CREATE TEMP TABLE`	Not supported
PostgreSQL	`CREATE TEMP TABLE`	Not native
MySQL	`CREATE TEMPORARY TABLE`	Not supported
SQL Server	`CREATE TABLE #name`	`CREATE TABLE ##name`
Oracle	Via GTT with session scope	`CREATE GLOBAL TEMPORARY TABLE`

When to Use TEMP Tables

Decision Framework

Quick Preview

Here's a preview of what working with temp tables looks like:

-- This query demonstrates the CONCEPT of temp tables
-- (We can't actually create temp tables in this read-only environment)

-- Imagine this as STEP 1: Create temp table with filtered data
-- CREATE TEMP TABLE temp_sp_customers AS
SELECT 
    customer_id,
    customer_unique_id,
    customer_city,
    customer_state
FROM olist_customers_dataset
WHERE customer_state = 'SP'
LIMIT 10;

-- Then STEP 2: Use the temp table in further analysis
-- SELECT * FROM temp_sp_customers ...

In the following lessons, we'll explore:

The exact syntax for creating temp tables
How databases execute temp table operations
Practical use cases for temp tables

Summary

Key Takeaways

Temp tables are session-scoped - They exist only during your database session
Automatic cleanup - No need to DROP; tables disappear when session ends
Session isolation - Other users cannot see your temp tables
Performance benefits - Often stored in memory, minimal logging
Use for intermediate work - Complex query steps, ad-hoc analysis, testing

Quick Comparison

Aspect	TEMP Table	Regular Table	CTE
Lifespan	Session	Permanent	Single query
Visibility	Session only	All users	Query only
Storage	Memory/temp	Disk	Memory
Cleanup	Automatic	Manual	Automatic
Reusable	Yes (in session)	Yes	Within query

What's Next?

Let's learn the TEMP Table Syntax for creating and using temporary tables.