5️⃣ 🗄️ MySQL Database Operations – Create, Manage & Maintain Databases and Tables

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🧲 Introduction – Why Learn MySQL Database Operations?

Before you can query data or build relationships between tables, you must understand how to create and manage your MySQL database architecture. MySQL provides a robust suite of DDL (Data Definition Language) commands that let you build, modify, and manage entire database structures with ease.

Whether you’re setting up a new application or evolving an existing system, these skills are essential for developers, DevOps engineers, and DBAs.

🎯 In this guide, you’ll learn:

• How to create, modify, and drop databases/tables
• Schema evolution with ALTER, TRUNCATE, and RENAME
• Adding indexes and constraints for optimization
• Best practices for safe and scalable database operations

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📘 Topics Covered

🔧 Topic	📄 Description
🏗️ MySQL Create / Drop Database	Start or remove complete databases
🔍 MySQL Select / Show / Copy DB	Set active DB, list metadata, or clone DB
📤 MySQL Export & Import Database	Backup or migrate databases using mysqldump and source
ℹ️ MySQL Database Metadata & Info	Query schema details and status using SHOW, DESCRIBE, and INFORMATION_SCHEMA

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🗄️ 1. Create a New Database

CREATE DATABASE company_db;

💡 Creates an empty database container.

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🧭 2. Select a Database to Use

USE company_db;

💡 Activates the selected DB for all upcoming operations.

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❌ 3. Drop (Delete) a Database

DROP DATABASE company_db;

⚠️ Permanently deletes the database and all its contents. Use with caution.

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📦 Table-Level Operations

🧱 4. Create a Table

CREATE TABLE employees (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(100),
  department VARCHAR(50),
  salary DECIMAL(10,2),
  hire_date DATE
);

💡 Defines structure and column types for storing employee data.

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🛠️ 5. Alter a Table – Add, Modify, or Drop Columns

-- Add a new column
ALTER TABLE employees ADD email VARCHAR(100);

-- Modify an existing column
ALTER TABLE employees MODIFY name VARCHAR(150);

-- Drop a column
ALTER TABLE employees DROP COLUMN department;

🔄 Useful for evolving schemas without dropping data.

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🏷️ 6. Rename a Table

RENAME TABLE employees TO staff;

📛 Renames the entire table.

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🧹 7. Truncate a Table

TRUNCATE TABLE employees;

⚠️ Deletes all rows but keeps the structure intact.

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🧾 8. Drop a Table

DROP TABLE employees;

💀 Completely removes the table and its contents.

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🧪 Constraints & Indexing

🔐 9. Add Constraints

-- NOT NULL
ALTER TABLE employees MODIFY name VARCHAR(100) NOT NULL;

-- UNIQUE
ALTER TABLE employees ADD UNIQUE (email);

-- FOREIGN KEY
ALTER TABLE orders
ADD CONSTRAINT fk_customer
FOREIGN KEY (customer_id) REFERENCES customers(id);

🛡️ Enforce business rules at the DB level.

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⚡ 10. Add Indexes for Performance

CREATE INDEX idx_salary ON employees(salary);

🚀 Improves SELECT and JOIN performance.

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📄 DDL Command Reference

🔤 Command	🔍 Purpose
CREATE	Make new database, table, index, etc.
ALTER	Change existing table structure
DROP	Remove database/table/index
TRUNCATE	Delete all rows without dropping structure
RENAME	Rename table or DB object

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🚀 Real-World Use Cases

🧩 Scenario	🛠️ SQL Operation(s) Used
Set up new app DB	CREATE DATABASE, CREATE TABLE
Add new column to support UI	ALTER TABLE ADD
Remove deprecated feature	DROP TABLE, DROP COLUMN
Reset dev/test data	TRUNCATE TABLE
Improve slow queries	CREATE INDEX, ALTER TABLE ADD INDEX

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📘 Best Practices for Database Operations

✅ Tip	💡 Why It Matters
Use IF EXISTS / IF NOT EXISTS	Prevents runtime errors
Always backup before DROP/TRUNCATE	These actions are irreversible
Favor ALTER over drop/create	Preserves data integrity
Use clear, consistent naming	Helps with team collaboration
Review index impact	Speeds up SELECT but slows down INSERT/UPDATE

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📌 Summary – Recap & Next Steps

MySQL database operations form the backbone of backend and data infrastructure. With commands like CREATE, ALTER, DROP, and indexing strategies, you can efficiently build and manage your data architecture across any environment.

🔍 Key Takeaways:

• Use DDL commands (CREATE, ALTER, DROP) to manage schema
• Use TRUNCATE to clear data fast while keeping structure
• Apply constraints and indexes to enforce logic and boost performance
• Use caution with irreversible commands like DROP

⚙️ Real-World Relevance
These operations are essential for DBAs, backend engineers, and DevOps professionals involved in deploying and maintaining scalable, efficient database systems.

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❓ FAQ – MySQL Database Operations

❓ What’s the difference between DROP and TRUNCATE?

• DROP removes the entire table structure
• TRUNCATE clears data but retains the schema

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❓ Can I rename a column directly?
✅ Yes. Use:

ALTER TABLE employees CHANGE old_name new_name VARCHAR(100);

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❓ Is it possible to undo a DROP DATABASE command?
❌ No. The operation is irreversible unless you have a backup.

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❓ Does ALTER TABLE keep the existing data?
✅ Yes, unless you explicitly drop or change data types incompatibly.

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❓ What’s the safest way to evolve a table structure?
✅ Use ALTER TABLE in small, incremental changes and always test in a staging environment.

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