Motivation Q: Why learn a database lanugage? A programming language allowing multiple concurrent users storing, manipulating, and querying data stored in a relational database. Data john fox applied regression analysis and generalized linear models pdf not necessary have to fit into memory. Different Implementations of SQL MySQL: Highly popular open source SQL implementation.
Database is saved as a single file and only allows one writer at a time. Oracle: SQL implementation produced and marketed by Oracle Corporation. The database used by University of Waterloo. An individual piece of data stored in a table.
A tuple of columns describing an entity or action of an entity. Result set: A non-persistent table, usually the result of a query. View: A named query saved into memory and performed whenever it is named. Subquery: A query that returns a table to another query.
Primary key: A tuple of columns that uniquely define each row in a table. Foreign key: A tuple of columns identifying a relationship to another table. Model is an analysis tool for relational databases. E refers to entity: An object R refers to relationship: As in how objects relate to each other. Each entity has properties associated with every instance of an object. One to many relationships: For every instance of object A, there are an indeterminate number of instances of object B.
Many to one relationships: For many instances of object A, there are a single instance of object B. Many to many relationships: For many instances of object A, there are a many possible instances of object B. Normalization Database Normalization is a process in relational databases to minimize redundacy. Data can be constructed so that additions, deletions, and modifications can be made in just one table. First Normalized Form: Each attribute contains only atomic values and only a single value from that domain. The data is in the form of a table with no merged columns or rows. Third Normalized Form: All non-primary key attributes are not determined by any other non-primary key attributes.