Database Study

recovery manager

ensures the atomicity and durability properties

Query evaluation engine

executes low-level instructions generated by the DML compiler

The overall design of the database is called the database

schema

To access the database, DML statements need to be

sent from the host to the database where they will be executed

At the physical level, an instructor, department, or student record can be described as

a block of consecutive bytes

data model

a collection of conceptual tools for describing data, data relationships, data semantics, and consistency constraints

A database-management system (DBMS)

a collection of interrelated data and a set of programs to access those data

A transaction is

a collection of operations that performs a single logical function in a database application

logical schema

a describes the database design at the logical level

The front end communicates with an

application server

Database systems are used to manage collections of data that:

are highly valuable, are relatively large, and are accessed by multiple users and applications, often at the same time.

Early databases were maintained as

back-office systems with which users interacted via printed reports and paper forms for input

Indices

can provide fast access to data items

database

collection of data that contains information relevant to an enterprise

Application programmers

computer professionals who write application programs

Domain constraints are

the most elementary form of integrity constraint

physical-design phase

the physical features of the database are specified

Referential Integrity

ensures that a value that appears in one relation for a given set of attributes also appears in a certain set of attributes in another relation

data analytics

the processing of data to draw conclusions, and infer rules or decision procedures, which are then used to drive business decisions

Transaction manager

ensures that the database remains in a consistent (correct) state despite system failures, and that concurrent transaction executions proceed without conflicts

Object-Based Data Model

A data model that uses objects to organize spatial data and stores geometries and attributes in a single system

Domain Constraints

A domain of possible values must be associated with every attribute

three-tier architecture

where the client machine acts as merely a front end and does not contain any direct database calls

Physical Data Independence

Although implementation of the simple structures at the logical level may involve complex physical-level structures, the user of the logical level does not need to be aware of this complexity

The query processor components include:

DDL interpreter, DML compiler, and the Query evaluation engine

The storage manager translates the various

DML statements into low-level file-system commands

major disadvantages of keeping organizational information in a file-processing system

Data redundancy and inconsistency, Difficulty in accessing data, Data isolation, Integrity problems, Atomicity problems, Concurrent-access anomalies, and Security problems

types of database-system users

Naıve users, Application programmers, Sophisticated users

View level

The highest level of abstraction describes only part of the entire database.

Physical level

The lowest level of abstraction that describes how the data are actually stored

Logical level

The next-higher level of abstraction that describes what data are stored in the database, and what relationships exist among those data

query language

The portion of a DML that involves information retrieval

A data-manipulation language (DML) is

a language that enables users to access or manipulate data as organized by the appropriate data model

normalization

a set of algorithms that takes as input the set of all attributes and generates a set of tables

We specify a database schema by

a set of definitions expressed by a special language called a data-definition language (DDL)

A query is

a statement requesting the retrieval of information

distributed databases

allow data storage and query processing across multiple geographically separated machines

abstraction

allows a person to use a complex device or system without having to know the details of how that device or system is constructed

delete authorization

allows deletion of data

insert authorization

allows insertion of new data, but not modification of existing data

update authorization

allows modification, but not deletion, of data

read authorization

allows reading, but not modification, of data

Modern database systems exploit commonalities in the structure of data to gain efficiency but

also allow for weakly structured data and for data whose formats are highly variable

transaction manager

consists of the concurrency-control manager and the recovery manager

concurrency-control manager

controls the interaction among the concurrent transactions, to ensure the consistency of the database

A database schema

corresponds to the variable declarations (along with associated type definitions) in a program

metadata

data about data

The output of the DDL is placed in the

data dictionary

The Java Database Connectivity (JDBC) standard

defines a corresponding interface for the Java language.

The Open Database Connectivity (ODBC) standard

defines application program interfaces for use with C and several other languages

physical schema

describes the database design at the physical level

parallel databases

designed to run on a cluster consisting of multiple machines to scale up to even larger data volumes and even higher processing speeds

failure recovery

detect system failures and restore the database to the state that existed prior to the occurrence of the failure

Authorization

differentiates among the users as far as the type of access they are permitted on various data values in the database.

data-manipulation language (DML)

expresses database queries and updates

e data-definition and data-manipulation languages

form parts of a single database language, such as the SQL language

The physical schema

hidden beneath the logical schema

Databases use a type of data structure called an ____ to support efficient retrieval of records

index

The collection of information stored in the database at a particular moment is called an

instance

The values of the variables in a program at a point in time correspond to an ______ of a database schema.

instance

DDL interpreter

interprets DDL statements and records the definitions in the data dictionary

The buffer manager is a critical part of the database system, since

it enables the database to handle data sizes that are much larger than the size of main memory

query optimization

it picks the lowest cost evaluation plan from among the alternatives

File manager

manages the allocation of space on disk storage and the data structures used to represent information stored on disk

two modes in which databases are used

online transaction processing and data analytics

Semi-structured Data Model

permits the specification of data where individual data items of the same type may have different sets of attributes (JSON and Extensible Markup Language (XML))

a database index provides

pointers to those data items that hold a particular value

Application programs

programs that are used to interact with the database

conceptual-design phase

provides a detailed overview of the enterprise

Tables are also known as

relations

Declarative DMLs (also referred to as nonprocedural DMLs)

require a user to specify what data are needed without specifying how to get those data

Buffer manager

responsible for fetching data from disk storage into main memory, and deciding what data to cache in main memory

Procedural DMLs

s require a user to specify what data are needed and how to get those data

business logic

says what actions to carry out under what conditions, is embedded in the application server, instead of being distributed across multiple clients

data-definition language (DDL)

specifies the database schema

data storage and definition language

specifies the storage structure and accesses methods used by the database system by a set of statements in a special type of DDL

The DDL is also used to

specify additional properties of the data

Data files

store the database itself

Data dictionary

stores metadata about the structure of the database, in particular the schema of the database

the storage manager is responsible for

storing, retrieving, and updating data in the database

A database may also have several schemas at the view level that describe different views of the database sometimes called

subschemas

file-processing system is

supported by a conventional operating system

Authorization and integrity manager

tests for the satisfaction of integrity constraints and checks the authority of users to access data

storage manager

the component of a database system that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system

Database design mainly involves

the design of the database schema

logical-design phase

the designer maps the high-level conceptual schema onto the implementation data model of the database system that will be used

The storage manager is responsible for

the interaction with the file manager

The functional components of a database system can be broadly divided into

the storage manager, the query processor components, and the transaction management component

The primary goal of a DBMS is

to provide a way to store and retrieve database information that is both convenient and efficient.

DML compiler

translates DML statements in a query language into an evaluation plan consisting of low-level instructions that the query-evaluation engine understands

We may describe the type of a record abstractly as follows:

type instructor = record ID : char (5); name : char (20); dept name : char (20); salary : numeric (8,2); end;

Non-procedural query languages such as SQL are not as powerful as a

universal Turing machine

Naıve users

unsophisticated users who interact with the system by using predefined user interfaces, such as web or mobile applications

specification of functional requirements

users describe the kinds of operations (or transactions) that will be performed on the data

Entity-Relationship (ER) Model

uses a collection of basic objects, called entities, and relationships among these objects

Relational Model

uses a collection of tables to represent both data and the relationships among those data

predictive models

uses data mining and predictive methods to forecast outcomes

Database modifications can cause

violations of referential integrity

online transaction processing

where a large number of users use the database, with each user retrieving relatively small amounts of data, and performing small updates (primary)

two-tier architecture

where the application resides at the client machine, and invokes database system functionality at the server machine through query language statements.