RELATIONAL DATABASE MANAGEMENT SYSTEMS (RDBMS

• RELATIONAL DATABASE (RDBMS)

  -          stores and provides access to data points that are related to one another.

  -          based on the relational model, straightforward way of representing data in tables.

  -          In a relational database, each row in the table is a record with a unique ID called the key. The columns of the table hold attributes of the data, and each record usually has a value for each attribute, making it easy to establish the relationships among data points.
• PROPERTIES OF RELATION

  1.        It has a unique name.

  2.       No multivalued attributes are allowed in a relation.

  3.       Each row is unique.

  4.      Each attribute has a unique name.

  5.      The sequence of columns as well as of rows is insignificant.
• CLASSIFICATION OF ATTRIBUTES

  Required – must have a value

  Optional – may not have a value
• CLASSIFICATION OF ATTRIBUTES

  o Simple (or atomic) - cannot be broken down into smaller components (ex. Age)

  o Composite – has meaningful component parts (ex. name - fname, mname, lname)
• CLASSIFICATION OF ATTRIBUTES

  o Single-valued – attribute which has only one value (ex. birthdate)

  o Multivalued Attributes – attribute that may take on more than one value (ex. phone number)
• CLASSIFICATION OF ATTRIBUTES

  o Stored – value is provided by user (ex. name)

  o Derived – value is computed or derived from another attribute/s (ex. age)
• IDENTIFIER

  -          an attribute or combination of attribute whose value distinguishes instances of an entity type.

  o Must not change in value

  o Must not be null

  o Must be unique
• CLASSIFICATION OF ATTRIBUTES

  Required vs. Optional Attributes

  o Required: medical condition, attributes pertaining to co-morbidities

  o Optional: provincial address
• Entity Type 

  -          collection of entities that have the same attributes.
• Entity Set 

  -          collection of entities of a particular entity type at a point in time.
• Primary Key an attribute or a combination of attributes that uniquely identifies each row in a relation.
• COMPOSITE KEY 


   a primary key that consists of more than one attribute.
• Foreign Key

  • attribute used to establish the relationship between two tables. A foreign key in a table/relation always point to the primary key of another table/relation.
• INTEGRITY CONSTRAINTS

  -          Rules limiting acceptable values and actions, to facilitate maintaining the accuracy and integrity of data.
• Domain Constraints

  • a set of values that can be assigned to an attribute
  • consists of domain name, meaning, data type, size and allowable values for the domain values.
•  Entity Integrity


  ensures that every relation has a valid primary key.
• Referential Integrity

  • rule that maintains consistency among the rows of two relations. The rule states that if there is a foreign key, either each foreign key value must match a primary key value or the foreign key value must be null.