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CIS Exam 2

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Side ASide B
Entity
- is some identifiable thing that users want to track:
  • Customers
  • Computers
  • Sales
Attribute
describe an entity’s characteristics.All entity instances of a given entity class have...
DDL
Short for Data Definition Language, DDL...
Chen Notation
Entity relationship model
NULL
no legal or binding force; invalid.
Data
recorded facts and figures
Data Model
is a plan or blueprint for a database design.        
  • A...
DML
data Manipulation language   It is used to retrieve, store, modify, delete,...
Primary Key
  • - is a candidate key selected as the primary means of identifying rows in a...
aggregate functions
Aggregate functions perform a calculation on a set of values and return a single value. Except...
Join
- Join conditions can be specified in either the FROM or WHERE clauses
Table
organizes the information about a single topic into rows and columns
Relationship
Entities can be associated with one another
Tuple
 tuple uniquely identifies a slice of data from a cube. The tuple is formed by a combination...
Derived Attributes
- are attributes whose values are generated from other attributes---Something u can calculate...
Mandatory Participation
IF you see a vertical hash mark THEN that entity is mandatory (required) (minimum cardinality...
SQL
Structured Query Language is an internationally recognized standard database language that...
Candidate Key
is a key that determines all of the other columns in a relation.
Foreign Key
  • is the primary key of one relation that is placed in another relation to form...
ER Model
a set of concepts and graphical symbols that can be used to create conceptual schemas.
Relation
  • - is a two-dimensional table that has the following characteristics:
    • Rows...
Composite Key
is a key that consists of two or more columns.
Functional Dependency
occurs when the value of one (set of) attribute(s) determines the value of a second (set of)...
Identifier
- are attributes that name, or identify, entity instances. The identifier of an entity instance...
Surrogate Key
- is an artificial column added to a relation to serve as a primary key.
  • DBMS...
Key
is a combination of one or more columns that is used to identify rows in a relation.
Codds Rules
—A Relational Database: —Rows contain data about one entity —Columns contain...
DBMS
—The Database Management System (DBMS) creates, processes, and administers databases.
Primary key
is a candidate key selected as the primary means of identifying rows in a relation.
  • There...
Identifiers
•Identifiers are attributes that name, or identify, entity instances. •The...
Composite identifiers
are identifiers that consist of two or more attributes.
Cardinality
means “count,” and is expressed as a number. •Maximum cardinality is the...
recursive relationship
occurs when an entity has a relationship to itself
Data redundancy- Why is it a problom
it creates redundancy, fix it by normalization
Super Key
group of all possible keys
View
Snap shot of database at one given point
Modification Anomaly (Three kinds)-
update, delete, insert


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