What are the different types of datasets (e.g., structured, unstructured, semi-structured)?

Datasets are categorized into three main types based on their organization and format: structured, unstructured, and semi-structured. Structured data follows a fixed schema, often stored in tables with rows and columns, like relational databases (e.g., SQL tables). Each field has a predefined data type, making it easy to query and analyze. Unstructured data lacks a specific format and includes text, images, videos, or sensor data. Examples include social media posts or raw log files. Semi-structured data sits between the two, with some organizational markers (like tags or keys) but no rigid schema. JSON, XML, and CSV files fall into this category. These distinctions matter because they influence how developers store, process, and analyze data.

Structured data is the most straightforward to work with due to its predictable format. For example, a customer database might store names as strings, order dates as timestamps, and prices as decimals. Developers typically use SQL for querying or tools like PostgreSQL or MySQL for storage. Unstructured data, on the other hand, requires specialized tools. A video file or a collection of tweets can’t be directly queried with SQL—instead, developers might use NoSQL databases like MongoDB for storage or frameworks like Apache Spark for processing. Semi-structured data, such as a JSON response from an API, offers flexibility: fields can vary between records, but keys (like “user_id” or “timestamp”) provide some structure. This makes it common in web applications and IoT systems, where data formats evolve over time.

The choice of dataset type impacts development workflows. Structured data works well for transactional systems (e.g., banking apps) where consistency is critical. Unstructured data is common in machine learning pipelines—for instance, training image recognition models requires raw image files. Semi-structured data is ideal for scenarios where schemas change frequently, like logging systems where new event types may emerge. Developers often convert semi-structured data into structured formats for analysis (e.g., parsing JSON logs into SQL tables). Tools like Python’s pandas library or Apache Avro help bridge gaps between these types. Understanding these categories ensures developers select the right storage solutions, query languages, and processing frameworks for their projects.