MSCI 2130 Chapter Notes - Chapter 3: Conceptual Schema, Data Manipulation Language, Data Definition Language
3 Jul 2019
School
Department
Course
Professor
Document Summary
Structured query language (sql: sql is a virtually universal language for interacting with databases, two aspects of sql. Data definition language (ddl: instructions and commands used to define and describe data and relationships. Data manipulation language (dml: allows users to access and modify data, make queries, and generate reports, query by example (qbe) provides a user friendly interface for generating sql queries. A diagram of data entities and their relationships: entity-relationship (er) diagram. Conceptual data model that graphically depicts the organization of and relationships between data. Driven by business rules and supported by a data dictionary: three types of relationships are possible between the entities in an er diagram. Cardinality: maximum number of times an instance of one entity can be associated with an instance in a related entity. Can be mandatory single, optional single, mandatory many, or optional many. Normalization: a technique to improve efficiency of complex databases by eliminating redundant data.
