ISYS114 Lecture Notes - Lecture 4: Multivalue, Referential Integrity, Data Integrity

• School: Macquarie University
• Department: Information Systems
• Course: ISYS114
• Professor: Charanya

Document Summary

Data structure tables (relations), rows, columns, data manipulation powerful sql operations for retrieving and modifying data, and data integrity mechanisms for implementing business rules that maintain integrity for manipulated data. A relation is a named, two-dimensional table of data. A table consists of rows (records) and columns (attribute or field). Note: all relations are in 1st normal form. Relations (tables) correspond with entity types and with many-to-many relationship types. Rows correspond with entity instances and with many-to-many relationship instances. Note: the word relation (in relational database) is not the same as the word relationship (in er model). Keys are special fields that serve two main purposes: primary keys are unique identifiers of the relation. Examples include employee numbers, social security numbers, etc. Foreign keys are identifiers that enable a dependent relation (on the many side of a relationship) to refer to its parent relation (on the one side of the relationship).