Basic CRUD Operations

This tutorial covers the fundamental Create, Read, Update, and Delete (CRUD) operations in yourdb. We'll use a simple Product class as an example.

Setup

First, let's define our data model and set up the database entity.

from yourdb import YourDB, register_class

# 1. Define the data model
@register_class
class Product:
    __version__ = 1
    def __init__(self, name, price, category):
        self.product_id = None # Primary key, set during insert
        self.name = name
        self.price = price
        self.category = category

    def __repr__(self):
        return f"Product(id={self.product_id}, name='{self.name}', price=${self.price}, cat='{self.category}')"

# 2. Initialize the database
db = YourDB("inventory_db")

# 3. Define the schema
product_schema = {
    'primary_key': 'product_id',
    'product_id': "int",
    'name': "str",
    'price': "int",
    'category': "str",
    'indexes': ['category'] # Add an index for faster category lookups
}

# 4. Create the entity (like a table)
db.create_entity("products", product_schema)

Create (Insert)

To add new records, use the insert_into() method. You pass the entity name and the Python object you want to store. Remember to set the primary key ( product_id in this case) before inserting.

# Create product objects
laptop = Product(name="Laptop Pro", price=1500, category="Electronics")
laptop.product_id = 101 # Set the primary key

keyboard = Product(name="Mechanical Keyboard", price=120, category="Accessories")
keyboard.product_id = 102

desk = Product(name="Standing Desk", price=450, category="Furniture")
desk.product_id = 103

# Insert them into the database
db.insert_into("products", laptop)
db.insert_into("products", keyboard)
db.insert_into("products", desk)

print("Inserted 3 products.")

Read (Select)

To retrieve data, use the select_from() method.

• Calling it with just the entity name fetches all records.
• Providing a filter_dict allows you to query specific records based on their attributes.

# Read all products
print("--- All Products ---")
all_products = db.select_from("products")
for p in all_products:
    print(p)

# Read only products in the 'Electronics' category (uses the index)
print("\n--- Electronics Products ---")
electronics = db.select_from("products", {'category': 'Electronics'})
for p in electronics:
    print(p)

# Read a specific product by its primary key
print("\n--- Specific Product (ID 103) ---")
specific_product = db.select_from("products", {'product_id': 103})
if specific_product:
    print(specific_product[0])
else:
    print("Product not found.")

Update

To modify existing records, use the update_entity() method. It requires:

• The entity name.

• A filter_dict to identify which record(s) to update.

• An update_fn (a function or lambda) that takes the object found by the filter and modifies it directly.

    # Let's increase the price of the Standing Desk (ID 103)

        print("\n--- Updating Product Price ---")

        def increase_price(product_obj):
            product_obj.price += 50 # Modify the object directly
            print(f"Updated price for {product_obj.name} to ${product_obj.price}")
            return product_obj # Important: return the modified object

        db.update_entity(
            "products",
            {'product_id': 103}, # Filter: Find the desk
            increase_price         # Update function: Apply the price increase
        )

        # Verify the update
        updated_desk = db.select_from("products", {'product_id': 103})[0]
        print(f"Verified new price: ${updated_desk.price}")

Delete

To remove records, use the delete_from() method. It takes the entity name and a filter_dict to specify which records to delete.

    # Let's delete the keyboard (ID 102)

    print("\n--- Deleting Product ---")
    db.delete_from("products", {'product_id': 102})
    print("Deleted product with ID 102.")

    # Verify deletion
    remaining_products = db.select_from("products")
    print("\n--- Remaining Products ---")
    for p in remaining_products:
        print(p)