A car's ignition switch serves several purposes. First, it allows you to control the power to many of the car's accessories, preventing accessories from running down the car's battery when the car is parked for a long period of time.
Cardinality is the term used in database relations to denote the occurrences of data on either side of the relation. In the common data architecture, cardinality is documented with data integrity but not with data structure. There are several types of cardinality defining relationships between occurrences of entities on two sides of the line of relationships.
Redundancy is. 1  direct if a value is a copy of another. 2  indirect if the value can be derived from other values: 3  simplifies retrieval but complicates update. 4  conversely integration makes retrieval slow and updates easier. 5  Data redundancy can lead to inconsistency in the database unless controlled.