🚰 SQL TRUNCATE TABLE – Quickly Delete All Rows from a Table

🧲 Introduction – What is SQL TRUNCATE TABLE?

The TRUNCATE TABLE command in SQL is used to delete all rows from a table efficiently, while preserving the table’s structure, columns, and constraints. It’s often faster than DELETE and used for quick, irreversible cleanups.

🎯 In this guide, you’ll learn:

• Syntax and behavior of TRUNCATE TABLE
• Differences between DELETE, DROP, and TRUNCATE
• Performance implications and best use cases

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✅ 1. TRUNCATE TABLE Syntax

TRUNCATE TABLE table_name;

✅ Instantly removes all rows from the table.

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🔄 2. TRUNCATE vs DELETE vs DROP

Command	Deletes Data	Keeps Structure	Rollback Support	Affects Identity (Autoinc)
DELETE	✅	✅	✅ (if in transaction)	❌
TRUNCATE	✅	✅	❌ (some DBMS)	✅ (resets counter)
DROP TABLE	✅	❌	❌	❌

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🧪 3. Example – Truncate a Log Table

TRUNCATE TABLE audit_logs;

✅ Clears all records from audit_logs but keeps table definition intact.

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⚠️ 4. Behavior Notes

• Cannot truncate a table referenced by foreign key constraints
• Often faster than DELETE because it bypasses row-by-row logging
• May reset IDENTITY/AUTOINCREMENT fields depending on DBMS
• Not always rollback-safe (e.g., MySQL autocommit mode)

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📘 Best Practices

✅ Recommended	❌ Avoid This
Use for temp or staging table cleanup	Truncating tables with foreign keys
Test on a copy before production execution	Assuming rollback is possible
Pair with backup in live environments	Using in audit or production tables

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📌 Summary – Recap & Next Steps

TRUNCATE TABLE is a quick and efficient method to remove all records from a table. It’s best for non-critical, non-referenced tables where full deletion is required.

🔍 Key Takeaways:

• TRUNCATE is faster and cleaner than DELETE
• Keeps table structure, drops only the data
• May reset IDENTITY and bypass transactions

⚙️ Real-World Relevance:
Used in staging environments, ETL pipelines, testing frameworks, and log cleaning routines.

➡️ Next: Learn DROP TABLE to remove table structures or DELETE for selective row deletions.

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❓ FAQ – SQL TRUNCATE TABLE

❓ Does TRUNCATE remove the table?

❌ No. It removes all rows but keeps the table structure intact.

❓ Can I roll back a TRUNCATE?

✅ Depends on DBMS. PostgreSQL supports it in transactions. MySQL may not.

❓ Can I truncate a table with a foreign key?

❌ No. Most DBMS prevent it unless the key is dropped or disabled.

❓ Does TRUNCATE reset identity values?

✅ Yes, in SQL Server and PostgreSQL. MySQL depends on engine configuration.

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