📀 SQL TEMPORARY TABLES – Store Session-Specific Data

Introduction – What Are SQL Temporary Tables?

Temporary tables are special types of tables that exist only for the duration of a session or transaction. They are useful for storing intermediate results, processing temporary logic, and isolating data from permanent tables.

In this guide, you’ll learn:

• How to create, use, and delete temporary tables
• Differences between local and global temp tables
• Best practices and platform-specific syntax

1. CREATE TEMPORARY TABLE Syntax

-- MySQL / PostgreSQL
CREATE TEMPORARY TABLE temp_table_name (
  id INT,
  name VARCHAR(50)
);

-- SQL Server (local temp)
CREATE TABLE #temp_table (
  id INT,
  name VARCHAR(50)
);

The table exists only for the session or procedure.

2. Insert and Query from Temp Tables

INSERT INTO temp_table_name VALUES (1, 'Alice');
SELECT * FROM temp_table_name;

Use just like regular tables, but scoped to session.

3. Temp Table Lifecycle

4. Drop Temporary Table

DROP TEMPORARY TABLE temp_table_name;  -- MySQL / PostgreSQL
DROP TABLE #temp_table;                -- SQL Server

Optional, but good hygiene before session exit.

5. Temp Table Use Cases

• Break complex queries into steps
• Store session-level filters
• Stage intermediate results in ETL or reports
• Isolate test logic without altering permanent tables

Best Practices

Summary – Recap & Next Steps

Temporary tables are a flexible way to hold intermediate or volatile data safely within a session or procedure. They’re great for reporting, testing, and procedural logic.

Key Takeaways:

• Use CREATE TEMPORARY TABLE for session-level isolation
• Supported by MySQL, PostgreSQL, SQL Server (with different syntax)
• Auto-dropped when session ends (unless explicitly dropped earlier)

Real-World Relevance:
Used in testing, stored procedures, ETL pipelines, and advanced analytics.

FAQ – SQL Temporary Tables

What is a temporary table?

A table that lives only during the database session or transaction.

Do I need to drop temp tables manually?

Not strictly, but it’s a good habit for long-running sessions.

Can I use indexes on temp tables?

Yes. You can create indexes, constraints, and even joins.

How is a temp table different from a table variable or CTE?

Temp tables are real tables in memory/disk; variables and CTEs are lighter-weight alternatives.