Hierarchical Levels of Data in a Relational Database

In a relational database system, data stored in a DBMS is organized into several hierarchical levels. These levels provide structure and clarity, helping users manage and understand the data more effectively. Here's a breakdown of each level:

1. Character

   This is the most basic unit of data, consisting of individual symbols such as numbers (0–9), letters (A–Z, a–z), or special characters like *, &, %, #, and others.

2. Field (Attribute)

   A field represents a single data item or property within a record, such as "Name" or "Student ID (NIM)." Each field is assigned a specific name and data type. The actual content stored in a field is known as a data value. In table format, fields appear as columns.

3. Record (Tuple)

   A record, or tuple, is a collection of related fields that together describe one complete unit of data—often representing a real-world object or individual. For instance, a student record might include values for name, phone number, department, and address. In a database table, records are shown as rows.

4. Table (Entity)

   An entity is any object or concept that can be distinctly identified and has data stored about it in the database. In practice, entities are represented as tables, each comprising multiple records (rows) and fields (columns). For example, in an academic database system, common entities include students, lecturers, and courses. Traditionally, in older database systems, these were also referred to as files.

   Key characteristics of a table include:

   • Each record must be unique—duplicates are not allowed.

   • The order of records is not significant; data can be sorted as needed.

   • Field names must be distinct from one another.

   • Every field should have a defined data type and set of properties.

Reference:

• Ruliah, Suryadi Andri. Basis Data, 2024.