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Simplifying SQL DELETE for Developers: Syntax and Best Practices

Deleting data in SQL is common but risky. One mistake and you could drop all rows in a table. This guide provides a practical reference for using DELETE safely.

SQL DELETE Quick Reference

Basic syntax 

DELETE FROM table_name WHERE condition;
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Omitting WHERE deletes everything.

Return deleted rows (PostgreSQL) 

DELETE FROM users WHERE active = false RETURNING *;
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Examples

Delete inactive users:

DELETE FROM users WHERE last_login < NOW() - INTERVAL '6 months';
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Delete rows with NULL values:

DELETE FROM items WHERE description IS NULL;
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Best Practices

  1. Always use WHERE.
  2. Test with SELECT before deleting.

  3. Use transactions for large deletes:

    BEGIN;
DELETE FROM logs WHERE created_at < '2024-01-01';
COMMIT;

  4. Backup production data.

  5. Be cautious with cascading deletes.

FAQ

Delete all rows? 

DELETE FROM table_name;
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Can DELETE affect multiple tables?

No. Use multiple statements or foreign key cascades.

Safe way to test? 

SELECT * FROM table_name WHERE condition;
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Conclusion

SQL DELETE is powerful but demands caution. Use WHERE filters, transactions, and backups to protect your data. For more advanced examples and edge cases, read the article The SQL DELETE Statement Explained for more insights.

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