SDP_Lab_1_To-do-app/docs/DATABASE_DESIGN.md

Database Design Documentation

Overview

This project uses SQLite as a local-first, single-user relational database engine via the better-sqlite3 driver for Node.js.

Table Schema: tasks

CREATE TABLE IF NOT EXISTS tasks (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    title TEXT NOT NULL,
    description TEXT,
    due_date TEXT NOT NULL,
    topic TEXT NOT NULL,
    status TEXT CHECK(status IN ('Todo','In-Progress','Complete')) NOT NULL DEFAULT 'Todo',
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    is_archived BOOLEAN NOT NULL DEFAULT 0
);

Field Specifications

Column Name	Data Type	Constraints	Description
id	INTEGER	PRIMARY KEY AUTOINCREMENT	Unique identifier for each task record.
title	TEXT	NOT NULL	Short summary title of the task.
description	TEXT	Optional	Extended notes or detailed instructions for the task.
due_date	TEXT	NOT NULL	Due date formatted as ISO string (YYYY-MM-DD).
topic	TEXT	NOT NULL	Categorical topic tag (e.g. SDP, Personal).
status	TEXT	CHECK(status IN ('Todo','In-Progress','Complete'))	Current lifecycle state of the task. Default is 'Todo'.
created_at	TIMESTAMP	DEFAULT CURRENT_TIMESTAMP	System timestamp recorded on task creation.
is_archived	BOOLEAN	DEFAULT 0	Soft-deletion flag. 0 indicates active, 1 indicates archived.

Schema Design Decisions

1. Soft-Deletion (Archiving): Tasks are never permanently deleted from the database. Setting is_archived = 1 retains all historical data while hiding archived tasks from active views.
2. Dynamic Overdue State: The database schema explicitly excludes an is_overdue column. Storing is_overdue in a database column creates stale data when dates pass. Overdue status is dynamically computed at read-time by comparing due_date against the current date for non-completed tasks.