Custom In-Memory Database

This project is a homework assignment focused on implementing a Query Language inspired by SQL, built upon a custom in-memory database.

The goal is to implement operations on individual tables as well as interactions between multiple tables, allowing for complex data manipulation and querying.

Features

This project implements a lightweight database engine with the following capabilities:

Table Operations

• Insert: Add new rows to a table.
• Delete: Remove rows from a table.
• Sort: detailed sorting of table data by column.
• Select: Project specific columns from a table.
• Filter: Apply complex conditions to filter rows.
• Join: Perform inner/outer joins between two tables.
• Cartesian Product: Generate the Cartesian product of two tables.

Database Operations

• Manage Tables: Create, retrieve, and delete tables within a database instance.

Query Language

The project includes a domain-specific language (DSL) for filtering data:

• Filter Conditions: Equal, And, Or, Not.
• Complex Queries: Pre-defined queries for common use cases (e.g., finding customers by age and city, filtering orders by date).

Project Structure

• src/main/scala/Table.scala: Core data structure representing a database table.
• src/main/scala/Database.scala: Manages a collection of tables.
• src/main/scala/FilterCond.scala: Defines the filtering logic and conditions.
• src/main/scala/Queries.scala: Contains specific business logic queries.
• src/test/scala/: Contains unit tests for the application.

Prerequisites

• Scala: Version 3.3.1 or higher.
• sbt: The Scala Build Tool. Install sbt.

Note: This environment does not have sbt pre-installed. You will need to install it to build and run the project.

Installation & Usage

1. Clone the repository:

   git clone <repository_url>
   cd tema2

2. Run Tests: Execute the unit tests to verify the implementation.

   sbt test

3. Run the Application: You can use the sbt console to interact with the code:

   sbt console

   Then, inside the REPL:

   import Table._
   import Database._
   
   val db = Database(List())
   val newDb = db.insert("Users")
   println(newDb)

Examples

Creating a Table from CSV

val csvData = """
name,age,city
Alice,30,New York
Bob,25,Los Angeles
"""
val table = Table.fromCSV(csvData)

Filtering Data

import FilterCond._

// Assuming 'table' exists
val filter = Field("age", _.toInt > 20)
val filteredTable = table.filter(filter)