Relational Model                

• The relational model is based on a mathematical concept of a relation.
  It is a two dimensional-table, consisting of rows and a fixed number of named columns of data.
  
• In a relation, a row represents a collection of related data values. These values correspond to a real world entity or relationship.
  
• The table name and column names explain the values in each row. Each column must have a unique name and a data type.

Tables (Relation)

• Table is also called as Relation  


• It is a two dimensional-table, consisting of rows and a fixed number of named columns of data.                   


• Each relation (or table) in a database has a unique name.


• An entry at the intersection of each row and column is atomic (Cannot divide in to further components within the relation). Cannot have multi-valued attributes.


• Two rows in a relation are not identical. Each row is unique.


• Each attribute (or column) within a table has a unique name.

• In an Relation (table) columns are represented Fields


• Its also called as Attribute


• An attribute is an ordered pair of attribute name (column header) and type (domain or data type) name.


• An attribute value is a specific valid value for the type of the attribute.


• The columns of a relation can be interchanged without changing the meaning or use of the relation. Each attribute has a unique name.

Records

• In an Relation (table) raws are represented Records


• It also call as Tuples


• A tuple is an unordered set of attribute values.


• Two rows in a relation are not identical.


• Tuples in a relation don’t have any particular order.

Key Field

• A key field is a field or set of fields of a database table which together form a unique identifier for a database record (a table entry).


• The aggregate of these fields is usually referred to simply as "the key". A Key fields also define searches

Unique Key