Python MongoDB Create Database

Database Creation Concepts

# Database created when first document inserted
db = client["newstore"]
collection = db["products"]

# Valid names
db1 = client["mystore"]
db2 = client["user_data"]
db3 = client["app2024"]

# List all databases
db_list = client.list_database_names()
print("Databases:", db_list)

# Check if database exists
if "mystore" in client.list_database_names():
    print("Database exists!")

🔨 Creating a Database

MongoDB creates databases automatically when you first insert data

🔹 Basic Database Creation

import pymongo

# Connect to MongoDB
client = pymongo.MongoClient("mongodb://localhost:27017/")

# Access/create database
db = client["bookstore"]

# Database is not actually created until you insert data
print(f"Database object created: {db.name}")

# Check if database exists (will be False until data is inserted)
db_exists = "bookstore" in client.list_database_names()
print(f"Database exists on server: {db_exists}")  # False

# Insert first document to actually create the database
books = db["books"]
first_book = {"title": "Python Guide", "author": "John Smith", "price": 29.99}
result = books.insert_one(first_book)

# Now database exists
db_exists = "bookstore" in client.list_database_names()
print(f"Database exists after insert: {db_exists}")  # True

🔹 Multiple Database Creation

# Create multiple databases by inserting data
client = pymongo.MongoClient("mongodb://localhost:27017/")

# Create inventory database
inventory_db = client["inventory"]
products = inventory_db["products"]
products.insert_one({"name": "Laptop", "stock": 50})

# Create users database  
users_db = client["users"]
customers = users_db["customers"]
customers.insert_one({"name": "Alice", "email": "[email protected]"})

# Create orders database
orders_db = client["orders"]
orders = orders_db["orders"]
orders.insert_one({"customer_id": 1, "total": 999.99})

print("Created 3 databases with initial data!")

📏 Database Naming Rules

MongoDB has specific rules for database names

# Good database names
good_names = [
    "mystore",
    "user_data", 
    "app2024",
    "inventory_system",
    "blogDB"
]

# Bad database names (avoid these)
bad_names = [
    "my store",      # Contains space
    "data/base",     # Contains slash
    "app.db",        # Contains dot
    "123store",      # Starts with number
    "admin"          # Reserved name
]

# Create databases with good names
client = pymongo.MongoClient("mongodb://localhost:27017/")

for name in good_names:
    db = client[name]
    # Insert dummy data to create database
    db["test"].insert_one({"created": True})
    print(f"✅ Created database: {name}")

print(f"Total databases: {len(client.list_database_names())}")

📋 Listing Databases

View and manage existing databases

🔹 List All Databases

import pymongo

client = pymongo.MongoClient("mongodb://localhost:27017/")

# Get list of database names
db_names = client.list_database_names()
print("Available databases:")
for db_name in db_names:
    print(f"  - {db_name}")

# Get detailed database information
db_info = client.list_databases()
print("\nDetailed database info:")
for db in db_info:
    print(f"Name: {db['name']}, Size: {db.get('sizeOnDisk', 'N/A')} bytes")

🔹 Check Database Existence

# Function to check if database exists
def database_exists(client, db_name):
    return db_name in client.list_database_names()

# Check multiple databases
databases_to_check = ["mystore", "inventory", "nonexistent"]

for db_name in databases_to_check:
    exists = database_exists(client, db_name)
    status = "✅ EXISTS" if exists else "❌ NOT FOUND"
    print(f"Database '{db_name}': {status}")

# Create database if it doesn't exist
def create_database_if_not_exists(client, db_name):
    if not database_exists(client, db_name):
        db = client[db_name]
        # Insert dummy document to create database
        db["_temp"].insert_one({"created": True})
        # Remove dummy document
        db["_temp"].delete_one({"created": True})
        print(f"✅ Created database: {db_name}")
    else:
        print(f"ℹ️ Database '{db_name}' already exists")

create_database_if_not_exists(client, "newstore")

🎯 Practical Example: E-commerce Setup

Create a complete database structure for an e-commerce application

import pymongo
from datetime import datetime

def setup_ecommerce_database():
    # Connect to MongoDB
    client = pymongo.MongoClient("mongodb://localhost:27017/")
    
    # Create main e-commerce database
    ecommerce_db = client["ecommerce_store"]
    
    # Create collections with sample data
    
    # 1. Products collection
    products = ecommerce_db["products"]
    sample_products = [
        {"name": "Laptop", "price": 999.99, "category": "Electronics", "stock": 25},
        {"name": "Book", "price": 19.99, "category": "Education", "stock": 100},
        {"name": "Shirt", "price": 29.99, "category": "Clothing", "stock": 50}
    ]
    products.insert_many(sample_products)
    
    # 2. Customers collection
    customers = ecommerce_db["customers"]
    sample_customers = [
        {"name": "John Doe", "email": "[email protected]", "joined": datetime.now()},
        {"name": "Jane Smith", "email": "[email protected]", "joined": datetime.now()}
    ]
    customers.insert_many(sample_customers)
    
    # 3. Orders collection
    orders = ecommerce_db["orders"]
    sample_order = {
        "customer_email": "[email protected]",
        "items": [{"product": "Laptop", "quantity": 1, "price": 999.99}],
        "total": 999.99,
        "date": datetime.now(),
        "status": "pending"
    }
    orders.insert_one(sample_order)
    
    # Verify database creation
    if "ecommerce_store" in client.list_database_names():
        print("✅ E-commerce database created successfully!")
        
        # Show collections
        collections = ecommerce_db.list_collection_names()
        print(f"📁 Collections created: {collections}")
        
        # Show document counts
        print(f"📊 Products: {products.count_documents({})}")
        print(f"📊 Customers: {customers.count_documents({})}")
        print(f"📊 Orders: {orders.count_documents({})}")
    
    return ecommerce_db

# Run the setup
db = setup_ecommerce_database()