Hypothetical e-commerce database

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Certainly! Let's provide examples for each of the concepts you mentioned using a hypothetical e-commerce database scenario.

1. Normalization and Denormalization:

Normalization:

-- Normalized tables
CREATE TABLE Customers (
    customer_id INT PRIMARY KEY,
    customer_name VARCHAR(255),
    -- Other customer-related fields
);

CREATE TABLE Orders (
    order_id INT PRIMARY KEY,
    customer_id INT,
    order_date DATE,
    -- Other order-related fields
    FOREIGN KEY (customer_id) REFERENCES Customers(customer_id)
);

-- This is a normalized structure where customer information is in a separate table.

Denormalization:

-- Denormalized table
CREATE TABLE DenormalizedOrders (
    order_id INT PRIMARY KEY,
    customer_name VARCHAR(255),
    order_date DATE,
    -- Other denormalized order-related fields
);

-- In this denormalized structure, customer information is duplicated within the Orders table for better query performance.

2. Query Optimization:

-- Example of query optimization using indexing
CREATE INDEX idx_orders_customer_id ON Orders(customer_id);

-- This index improves the performance of queries that involve filtering or sorting by the customer_id column.

3. Transaction Management:

-- Example of transaction management
BEGIN TRANSACTION;

-- Update the order status
UPDATE Orders SET status = 'Shipped' WHERE order_id = 123;

-- Deduct the product quantity from inventory
UPDATE Products SET quantity = quantity - 1 WHERE product_id = 456;

-- If both updates succeed, commit the transaction
COMMIT;

-- If any update fails, roll back the entire transaction
ROLLBACK;

4. Database Security:

-- Example of role-based access control
CREATE ROLE Customer;
CREATE ROLE Admin;

-- Grant privileges to roles
GRANT SELECT, INSERT, UPDATE, DELETE ON Orders TO Customer;
GRANT ALL PRIVILEGES ON Orders TO Admin;

-- Assign roles to users
CREATE USER alice WITH PASSWORD 'password';
GRANT Customer TO alice;

5. Stored Procedures and Triggers:

-- Example of a stored procedure
CREATE PROCEDURE UpdateOrderStatus(IN order_id INT, IN new_status VARCHAR(50))
BEGIN
    UPDATE Orders SET status = new_status WHERE order_id = order_id;
END;

-- Example of a trigger
CREATE TRIGGER Before_Order_Insert
BEFORE INSERT ON Orders
FOR EACH ROW
SET NEW.order_date = NOW();

-- The trigger automatically sets the order_date to the current timestamp before inserting a new order.

These examples showcase how these concepts are implemented in SQL for a simplified e-commerce database. Keep in mind that the specifics may vary based on the actual database management system you are using (e.g., MySQL, PostgreSQL, etc.).