test 1 Flashcards
What is a Database Management System (DBMS)?
A suite of tools for creating and managing large
amounts of data efficiently and allowing it to
persist over long periods of time safely
What is a database?
A collection of data that is managed by a DBMS
What are the functions of a DBMS?
– Allow users to create new database and specify their schema
– Give users the ability to query the data
– Support the storage of very large amounts of data
– Enable durability, the recovery of the database in the face of
failures, errors of many kinds, or intentional misuse
– Control access to data from many users at once, without
allowing unexpected interaction among users and without
actions on the data to be performed partially but not
completely
What is Data-Defining Language (DDL)?
Used to define/altering
schema (structure) of
database.
What is Metadata?
Acts as a guide to reach data. Data about data
What is Data-Manipulation Language (DML)?
Modifies data
What are Constraints?
The define limitations on what data can be.
What are the operations on data?
- Query
- Modification
What is Structured data?
- Information stored DB
What is semi-structured data?
Data that may have certain structure but not all information collected has identical structure
What is unstructured data?
Very limited indication of data type.
What are the key differences between semi-structured and structured data?
- Semi-structured data is mixed in with its schema
- Sometimes known as self-describing data
- Can be displayed as a graph
- names of attributes, relationships, and
classes in the semi-structured data as
intermixed with their data values in the same
data structure - Semi-structured data has no requirement
for pre-defined schema to contain data
What kind of data has limited indication of data types?
Unstructured Data
What is an Entity?
An abstraction object
of some sort.
What is an entity set?
collection of similar entities.
What is an attribute?
property of (the entities of) an entity set.
What are relationships in entities?
connections among two or more entity sets.
What is the current “value” of an entity set?
The set of entities that belong to it.
What is a Many to Many (M:N) relationship?
an entity of either set can be connected to many entities of the other set.
What is a One to Many (1:M) relationship?
An entity of one set is connected to at least one, but the other set has many connections
What is a One to One (1:1) relationship?
each entity of either
entity set is related to at most one entity of the
other set.
What is Cardinality?
The number of instances participating in the relationships at anytime.
What conditions should an entity set satisfy?
– It is more than the name of something; it has at
least one non-key attribute.
or
– It is the “many” in a many-one or many-many
relationship
What is a key?
a set of attributes for one entity set such that no two entities in this set agree on all the attributes of the key.
What are degree constraints?
Limits on the number of entities that
can be connected to any one entity of
the related entity set
What makes a “weak” entity?
- Some entity sets fall into a hierarchy based on classifications unrelated to the “isa hierarchy”
- The connecting entity sets that eliminates a
multiway relationship
What are weak entity rules?
- A weak entity set has one or more many-one
relationships to other (supporting) entity sets. - The key for a weak entity set is its own underlined attributes and the keys for the supporting entity sets.
What is a degree of a relationship?
The number of entities connected by the relationship.
What is a recursive relationship?
refers to a relationship between entities of the same type.
Describe an archetype/instance relationship?
refers to the relationship between a general entity (the archetype) and specific occurrences of that entity (the instances).
Describe an “is-a” relationship?
indicates that one entity (a subclass or child) is a specialized form of another entity (a superclass or parent) and establishes a hierarchy where the child entity inherits the properties and behaviors of the parent entity.
What is a data model?
data structure on an entity?
What is a relational model?
data structure on a relation.
