PreQL is a lightweight, modular database management system written in modern C++. It provides a simple yet powerful interface for managing relational databases through SQL-like commands.

• SQL-like Interface: Support for basic SQL operations (CREATE, INSERT, SELECT, DELETE)
• Buffer Management: Efficient page management with buffer pool
• Table Management: Create, modify, and manage database tables
• Interactive CLI: User-friendly command-line interface
• Modern C++: Built with C++17 features and best practices

preql/
├── include/                 # Header files
│   ├── core/               # Core database functionality
│   ├── buffer/             # Buffer management
│   ├── sql/                # SQL parsing and processing
│   └── ui/                 # User interface
├── src/                    # Source files
│   ├── core/              # Database implementation
│   ├── buffer/            # Buffer manager implementation
│   ├── sql/               # Parser implementation
│   └── ui/                # CLI implementation
├── tests/                  # Test suite
│   ├── database_test.cpp  # Database tests
│   ├── buffer_test.cpp    # Buffer manager tests
│   ├── parser_test.cpp    # Parser tests
│   └── cli_test.cpp       # CLI tests
└── CMakeLists.txt         # Build configuration

• CMake (version 3.10 or higher)
• C++17 compatible compiler
• Google Test (for running tests)

1. Clone the repository:

   git clone https://github.com/yourusername/preql.git
   cd preql

2. Create a build directory:

   mkdir build
   cd build

3. Configure and build:

   cmake ..
   make

4. Run tests:

   make test

./preql

Basic table creation:

CREATE TABLE users (id INT, name VARCHAR, age INT)

Table with multiple columns and types:

CREATE TABLE products (
    id INT,
    name VARCHAR,
    price FLOAT,
    description VARCHAR,
    in_stock BOOLEAN
)

Single row insertion:

INSERT INTO users VALUES (1, 'John Doe', 25)

Multiple rows (execute each separately):

INSERT INTO users VALUES (2, 'Jane Smith', 30)
INSERT INTO users VALUES (3, 'Bob Johnson', 35)
INSERT INTO users VALUES (4, 'Alice Brown', 28)

Basic selection:

SELECT * FROM users

Select specific columns:

SELECT name, age FROM users

With conditions:

SELECT * FROM users WHERE age > 25

Complex conditions:

SELECT * FROM users WHERE age > 25 AND name LIKE 'J%'

UPDATE users SET age = 26 WHERE name = 'John Doe'

Delete specific records:

DELETE FROM users WHERE age < 30

Delete all records:

DELETE FROM users

View table structure:

DESCRIBE users

List all tables:

SHOW TABLES

1. Create a new database and tables:

CREATE TABLE employees (
    id INT,
    name VARCHAR,
    department VARCHAR,
    salary FLOAT,
    hire_date DATE
)

CREATE TABLE departments (
    id INT,
    name VARCHAR,
    location VARCHAR,
    manager_id INT
)

2. Insert sample data:

INSERT INTO employees VALUES (1, 'John Smith', 'Engineering', 75000, '2020-01-15')
INSERT INTO employees VALUES (2, 'Sarah Johnson', 'Marketing', 65000, '2019-06-01')
INSERT INTO employees VALUES (3, 'Michael Brown', 'Engineering', 80000, '2018-03-10')

INSERT INTO departments VALUES (1, 'Engineering', 'Floor 3', 1)
INSERT INTO departments VALUES (2, 'Marketing', 'Floor 2', 2)

3. Query the data:

-- Find all employees in Engineering
SELECT * FROM employees WHERE department = 'Engineering'

-- Find departments and their managers
SELECT d.name, e.name as manager_name 
FROM departments d 
JOIN employees e ON d.manager_id = e.id

-- Find average salary by department
SELECT department, AVG(salary) as avg_salary 
FROM employees 
GROUP BY department

4. Update records:

-- Give a raise to all Engineering employees
UPDATE employees 
SET salary = salary * 1.1 
WHERE department = 'Engineering'

5. Delete records:

-- Remove employees who left before 2020
DELETE FROM employees 
WHERE hire_date < '2020-01-01'

1. Database Core

   • Table management
   • Data storage and retrieval
   • Transaction handling

2. Buffer Manager

   • Page management
   • Buffer pool implementation
   • Page replacement policies

3. SQL Parser

   • SQL statement parsing
   • Query validation
   • Statement processing

4. CLI Interface

   • Command-line interface
   • User interaction
   • Result formatting

• PIMPL (Pointer to Implementation) for implementation hiding
• RAII for resource management
• Smart pointers for memory management
• Exception handling for error management

1. Fork the repository
2. Create a feature branch
3. Commit your changes
4. Push to the branch
5. Create a Pull Request

This project is licensed under the MIT License - see the LICENSE file for details.

• Modern C++ features and best practices
• Google Test framework for testing
• CMake build system