Study Notes Essay

Submitted By dashizzle
Words: 1464
Pages: 6

Many things may be done in sets – Union, Intersection, Difference, and Membership
Attributes – Entities are described by a set of attributes
Binary – if two domains
Can think of key as a constraint on a relation – to be unique, in that you cannot have more than one primary key
Candidate key – Set of attributes that form a key, no proper subset of this set of attributes forms a key. Can have many candidate keys only one can be a primary key – chosen to be that A superkey 2. Must also have the following attributes: no proper subset of a candidate key can be a key
Candidate key of R – Set of attributes that form a key, no proper subset of this set of attributes forms a key. Can have many candidate keys only one can be a primary key – chosen to be that
Cardinality of a set – tells how many things in set) (AKA Mapping cardinalities) – tells how many things in set, number of entities to which another entity can be associated via a relationship set, Cardinality of a relation is equal to the number of rows in that relation
Client-Server – can be used independently
Closed World Assumption – only base things on database not info logic outside of the database
Data Definition Language – something a database provides to specify the database schema
Data Manipulation Language – database queries and updates, - update relations, retrieve data from relations, check correctness of relations, inserts, deletes, Update relations, retrieve data from relations, check correctness of relations
Data Model – set of tools that will help you describe your data. Collection of tools to enable the description of enterprise data, constraints, semantics
Database – Collection of data related on an enterprise
Database Instance – Collection of data stored in each relation of database, actual instance of content of database, Instance of a database is instance of all relations in DB
Database Schema – Collection of relation schemas, definition of relations, like a class vs. an instance, schema of all relations in database
DBMS – Application that allows/provides access to database – Set of DDL and DML tools that describe the data of an enterprise, store it and retrieve it efficiently. Application that allows/provides access to database
Declarative – SQL is declarative because you don’t tell it what to do other than you say you want x from y table, require a user to specify what data are needed without specifying how to get the data
Decompose data - Legal decomposition or loss less decomposition does not lose any data and extra data does not appear
Design – attributes to stored, business decision – part time workers , Store as an attribute – or get via another means
Domains – Set of permitted values
Entities – Things in the Enterprise (nouns), independent, has attributes
Function – Mapping from domain to a range, For every value in domain, always another in range, Could be undefined
Generalization – Multiple entity sets are synthesized into a higher level entity set on the bases of common features
Instance – actual instance of content of database
Key A key is a subset of attributes that uniquely identify a row subset (c shape with line under it) of attributes, usually defined by people, should be minimal, Ensure no other can be a subset, For instance, customer name is minimal so it’s a candidate key, One candidate key is selected to be a primary key – Defined over a single relation, unique way of identifying a record in a relation, subset of attributes that can uniquely define a record, usually defined by people, should be minimal, can think of key as a constraint on a relation – to be unique, in that you cannot have more than one primary key
Logical Data Independence – Applications are independent from how the DBMS represent data. The storage method has no effect on its semantics
Metadata – data describing data
OLAP – Online analytical processing (more like for data mining)
OLTP – Online Transaction Processing - Means all databases