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.
Relational databases use tables to store information. The standard fields and records are represented as columns (fields) and rows (records) in a table. With a relational database, you can quickly compare information because of the arrangement of data in columns.The relational database model takes advantage of this uniformity to build completely new tables out of required information from existing tables.elational databases are created using a special computer language, structured query language (SQL) , that is the standard for database interoperability.