Uses of term Database table
The term table
takes on a dual meaning when we talk about database design. On the one hand, the elements comprising an ER diagram are referred to as base tables.
These are represented as
- entities and
- attributes, which represent the business objects
to be included in the database, and are the sort of tables during the process of relational database design.
They come into play during the Logical Design phase of the (DBLC) database lifye cycle.
We also use the term table to refer to the relational constructs comprising the implementation of the database.
These tables will be described in greater detail later in this module.
What are Base Tables
Question: What are the base tables within the context of Entity relationship diagrams?
In Entity-Relationship (ER) diagrams, base tables are the tables that represent the main entities or objects being modeled. Base tables contain the actual data and are the primary source of information in the database. Base tables are identified by rectangles in ER diagrams, with the name of the table written inside the rectangle. The attributes or columns of the table are listed within the rectangle, along with their data types and any constraints that apply to them.
Base tables are the foundation of an ER diagram and are used to represent the main entities being modeled. For example, in a university ER diagram, the base tables might include tables for students, courses, and instructors. Other tables in an ER diagram may be derived from base tables or used to represent relationships between base tables. For example, a table that links students to courses and represents enrollment data would be a derived table, as it is based on the relationship between the student and course base tables. Overall, base tables are the primary entities being modeled in an ER diagram and represent the main sources of data in the database. They are an essential component of the ER diagram and provide the foundation for the relationships and data structures represented in the diagram.
A table is a collection of related data held in a structured format within a database. It consists of fields (columns), and rows.
In relational databases, a table is a set of data elements using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows. Each row is identified by one or more values appearing in a particular column subset. The columns subset which uniquely identifies a row is called the primary key.
Table is another term for "relation", although there is a difference in that a table is usually a combination of rows where a relation is a set and does not allow duplicates. Besides the actual data rows, tables generally have associated with them metadata, such as constraints on the table or on the values within particular columns. The data in a table does not have to be physically stored in the database. Views also function as relational tables, however their data are calculated when a query is executed.