Lesson 4: The Relational Model (RDBMS) Terminology
The Relational Model, developed by E.F. Codd in 1970, is the theoretical basis for all RDBMSs. It uses mathematical logic to ensure data consistency.
Fundamental Terminology
It's important to know the formal (Relational Theory) terms and the practical (SQL/Database) terms:
| Concept | Formal Term (Theory) | Practical Term (SQL/Database) |
|---|---|---|
| The structure holding the data | Relation | Table |
| A single entry or record | Tuple | Row / Record |
| A specific field or attribute | Attribute | Column / Field |
| The overall structure of the table | Schema | Schema / Structure |
| A set of allowed values for a column | Domain | Data Type (e.g., Integer, Text, Date) |
Detailed Look at the Components:
- Tables (Relations): These are the primary storage units. A table consists of rows and columns.
- Rows (Tuples): Each row represents a single, complete entity or record (e.g., one specific customer, one specific order).
- Columns (Attributes): Each column holds a specific piece of information about the entity (e.g., customer name, customer ID, order date).
- Schema: This defines how the data is structured: the tables that exist, the columns within those tables, and the relationships between them.
Example Table (Employees)
| Employee_ID (Column) | Name (Column) | Department (Column) |
|---|---|---|
| 101 (Row) | Alice | Sales |
| 102 (Row) | Bob | HR |
In the next lesson, we will set up our environment to start practicing these concepts.