COE126 : Database Systems Flashcards
The overall logical structure of the database.
Logical Schema
The overall physical structure of database.
Physical Schema
The actual content of the database at a particular point in time.
Instances
The ability to modify the modify schema without changing the logical schema.
Physical Data Independence
Specification notation for defining the database schema
Data Definition Language (DDL)
ID uniquely identifies instructors
Primary Key
Language for accessing and updating the data organized by the appropriate data model. Also known as query model.
Data Manipulation Language (DML)
Require a user to specify what data are needed and how to get those data.
Procedural DML
Require a user to specify what data are needed without specifying how to get those data.
Declarative DML
__________ is nonprocedural. A query takes as input several tables (possibly only one) and always returns a single table.
SQL Query Language
Are programs that are used to interact with the database in this fashion.
Application Programs
Deciding on the database schema. It requires what we find a “good” collection of relation schemas.
Logical Design
Deciding on the physical layout of the database.
Physical Design
A database system in partitioned into modules that deal with each of the responsibilities of the overall system.
Database Engine
A program module that provides interface between the low-leveled data stored in the database and the application programs and queries submitted to the system.
Storage Manager
Interprets DDL statements and records the definitions in the data dictionary.
DDL interpreter
Translates DML statements in a query language into are evaluation plan consisting of low-level instructions that the query evaluation engine understands.
DML compiler
Executes low-level instructions generated by the DML compiler.
Query Evaluation Engine
A ___________ is a collection of operation that performs a single logical function in a database application.
transaction
Ensures that the database remain in a consistent (correct) state despite the failures and transaction failures.
Transaction-management component
Controls the interaction among the concurrent transaction, to ensure the consistency of the database
Concurrency-control manager
The application resides at the client machine, where it invokes database system functionality at the server machine.
Two-tier architecture
The client machine acts as a front end and does not contain any direct database calls.
Three-tier architecture
A person who has central control over the system is called
Database Administrator (DBA)
The set of allowed values of each attribute is called
Domain of the attribute
Is the logical structure of the database.
Database schema
is a snapshot of the data in the database at a given instant in time.
Database instance
A procedural language consisting of a set of operation that take one or two relations as input and produce a new relation as their result.
Relational Algebra
A unary operation that returns its argument relation, with certain attributes left out.
Project Operation
A real-world entity having properties called attributes.
Entity
Properties of entities that have values.
Attributes
Logical association among entities.
Relationship
Defines the number of association between two entities.
Cardinality
Attributes that uniquely identity rows of a table.
Candidate Key
The set of all the keys which help to identify rows in a table uniquely.
Super Key
Used to establish relationships between two tables.
Foreign Key
A set of two or more attributes that help identify each tuple in a table uniquely.
Composite Key
A table can have multiple choices for a primary key; however it can choose only one.
Alternate Key
A column or set of columns that uniquely identify each record in a table.
Unique Key
One entity has only one event shared with another entity.
One-to-One Cardinality (1:1)
One entity has an event that occurs one time, while the other entity can have more than one repetition of the event.
One-to-many Cardinality (1:n)
Opposite of one-to-many, difference is due to perspective.
Many-to-one Cardinality (m:1)
When both entities have the same event or relationship happen more than once.
Many-to-many Cardinality (m:n)
A graphical representation of the entity relationship model.
ER diagram
Is credited with introducing the widely adopted ER model in his paper “The Entity Relationship Model-Toward a Unified View of Data”.
Peter Chen
An entity that depends on the existence of another entity.
Weak Entity
An attribute that can have more than one value.
Multivalued Attribute
An attribute based on another attribute.
Derived Attribute
Describes how entities interact.
Relationship
If the same entity participates more than once in a relationship it is known as a
Recursive Relationship
Each entity in the entity set is involved in at least one relationship in a relationship set.
Total Participation
Each entity in the entity set may or may not occur in at least one relationship in a relationship set.
Partial Participation
