?Silberschatz,Korth and Sudarshan1.1Database System Concepts
DATABASE SYSTEM
CONCEPTS
instructor,Jingsheng Lei(雷景生 )
E-mail,jshlei@hainu.edu.cn
?Silberschatz,Korth and Sudarshan1.2Database System Concepts
Chapter 1,Introduction
? Applications of Database Systems
? Database Systems versus File Systems
? View of Data
? Data Models
? Database Language
? Database Users and Administrator
? Transaction Management
? Database System Structure
? Application Architectures
? History of Database Systems
? Summary
?Silberschatz,Korth and Sudarshan1.3Database System Concepts
Database Management System (DBMS)
? Collection of interrelated data.
? Set of programs to access the data,
? DB contains information about a particular enterprise.
? DBMS provides an environment that is both convenient
and efficient to use.
? Database systems are designed to manage large bodies
of information.
? DBS must ensure the safety of the information stored.
? Several users.
Data Database(DB) Database Management System
(DBMS) Database System(DBS)
?Silberschatz,Korth and Sudarshan1.4Database System Concepts
1 Applications of Database Systems
? Database Applications:
? Banking,all transactions
? Airlines,reservations,schedules
? Universities,registration,grades
? Sales,customers,products,purchases
? Manufacturing,production,inventory,orders,
supply chain
? Human resources,employee records,salaries,
tax deductions
? Databases touch all aspects of our lives
?Silberschatz,Korth and Sudarshan1.5Database System Concepts
2 Database Systems versus File Systems
In the early days,database applications were built on top of
file systems
? Drawbacks of using file systems to store data:
? Data redundancy and inconsistency
?Multiple file formats,duplication of information in different files
? Difficulty in accessing data
?Need to write a new program to carry out each new task
? Data isolation —multiple files and formats
? Integrity problems
?Integrity constraints (e.g,account balance > 0) become part of
program code
?Hard to add new constraints or change existing ones
?Silberschatz,Korth and Sudarshan1.6Database System Concepts
2 Database Systems versus File
Systems(Cont.)
? Drawbacks of using file systems (cont.)
? Atomicity of updates
?Failures may leave database in an inconsistent
state with partial updates carried out
?E.g,transfer of funds from one account to
another should either complete or not happen at
all
? Concurrent access by multiple users
?Concurrent accessed needed for performance
?Uncontrolled concurrent accesses can lead to
inconsistencies
–E.g,two people reading a balance and
updating it at the same time
? Security problems
?Silberschatz,Korth and Sudarshan1.7Database System Concepts
3 View of Data
3.1 Data Abstraction
? Physical level describes how a record (e.g.,customer) is
stored.
? Logical level,describes data stored in database,and the
relationships among the data.
type customer = record
name, string;
street, string;
city, integer;
end;
? View level,application programs hide details of data
types,Views can also hide information (e.g.,salary) for
security purposes,
?Silberschatz,Korth and Sudarshan1.8Database System Concepts
3 View of Data (Cont.)
An architecture for a database system
?Silberschatz,Korth and Sudarshan1.9Database System Concepts
3 View of Data (Cont.)
3.2 Instances and Schemas
? Similar to types and variables in programming
languages
? Schema – the logical structure of the database
? e.g.,the database consists of information about a
set of customers and accounts and the
relationship between them)
? Analogous to type information of a variable in a
program
? Physical schema,database design at the
physical level
? Logical schema,database design at the logical
level
?Silberschatz,Korth and Sudarshan1.10Database System Concepts
3 View of Data (Cont.)
? Instance – the actual content of the database at a
particular point in time
? Analogous to the value of a variable
? Physical Data Independence – the ability to
modify the physical schema without changing the
logical schema
? Applications depend on the logical schema
? In general,the interfaces between the various
levels and components should be well defined
so that changes in some parts do not seriously
influence others.
?Silberschatz,Korth and Sudarshan1.11Database System Concepts
4 Data Models
? A collection of tools for describing
? data
? data relationships
? data semantics
? data constraints
? Entity-Relationship model
? Relational model
? Other models,
? object-oriented model,object-relational data
model
? semi-structured data models
? Older models,network model and hierarchical model
?Silberschatz,Korth and Sudarshan1.12Database System Concepts
4.1 Entity-Relationship Model
Example of schema in the entity-relationship model
?Silberschatz,Korth and Sudarshan1.13Database System Concepts
4.1 Entity Relationship Model (Cont.)
? E-R model of real world
? Entities (objects)
?E.g,customers,accounts,bank branch
? Relationships between entities
?E.g,Account A-101 is held by customer Johnson
?Relationship set depositor associates customers
with accounts
? Widely used for database design
? Database design in E-R model usually converted to
design in the relational model (coming up next)
which is used for storage and processing
?Silberschatz,Korth and Sudarshan1.14Database System Concepts
4.2 Relational Model
? Example of tabular data in the relational model
customer-
nameCustomer-id
customer-
street
customer-
city
account-
number
Johnson
Smith
Johnson
Jones
Smith
192-83-7465
019-28-3746
192-83-7465
321-12-3123
019-28-3746
Alma
North
Alma
Main
North
Palo Alto
Rye
Palo Alto
Harrison
Rye
A-101
A-215
A-201
A-217
A-201
Attributes
?Silberschatz,Korth and Sudarshan1.15Database System Concepts
A Sample Relational Database
?Silberschatz,Korth and Sudarshan1.16Database System Concepts
5 Database Language
? 5.1 Data Definition Language (DDL)
? Specification notation for defining the database schema
?E.g,
create table account (
account-number char(10),
balance integer)
? DDL compiler generates a set of tables stored in a data
dictionary
? Data dictionary contains metadata (i.e.,data about data)
? database schema
?Data storage and definition language
– language in which the storage structure and
access methods used by the database system
are specified
–Usually an extension of the data definition
language
?Silberschatz,Korth and Sudarshan1.17Database System Concepts
5 Database Language (Cont.)
? 5.2 Data Manipulation Language (DML)
? Language for accessing and manipulating the data
organized by the appropriate data model
? Two classes of languages
?Procedural – user specifies what data is required
and how to get those data
?Nonprocedural – user specifies what data is
required without specifying how to get those data
? SQL is the most widely used query language
?Silberschatz,Korth and Sudarshan1.18Database System Concepts
5 Database Language (Cont.)
? 5.3 SQL
? SQL,widely used non-procedural language
?E.g,find the name of the customer with customer-
id 192-83-7465
select customer.customer-name
from customer
where customer.customer-id = ?192-83-
7465?
?E.g,find the balances of all accounts held by the
customer with customer-id 192-83-7465
select account.balance
from depositor,account
where depositor.customer-id = ?192-83-
7465? and depositor.account-number =
account.account-number
?Silberschatz,Korth and Sudarshan1.19Database System Concepts
5 Database Language (Cont.)
? Application programs generally access databases
through one of
? Language extensions to allow embedded SQL
? Application program interface (e.g,
ODBC/JDBC) which allow SQL queries to be
sent to a database
?Silberschatz,Korth and Sudarshan1.20Database System Concepts
6 Database Users AND Database
Administrator
? Database Users
? Application programmers – interact with system
through DML calls
? Sophisticated users – form requests in a database
query language
? Specialized users – write specialized database
applications that do not fit into the traditional data
processing framework
? Naive users – invoke one of the permanent
application programs that have been written
previously
?E.g,people accessing database over the web,
bank tellers,clerical staff
?Silberschatz,Korth and Sudarshan1.21Database System Concepts
6 Database Users AND Database
Administrator (Cont.)
? Database administrator's duties include:
? Schema definition
? Storage structure and access method definition
? Schema and physical organization modification
? Granting user authority to access the database
? Routine maintenance
?Silberschatz,Korth and Sudarshan1.22Database System Concepts
7 Transaction Management
? A transaction is a collection of operations that
performs a single logical function in a database
application
? Transaction-management component ensures that the
database remains in a consistent (correct) state
despite system failures (e.g.,power failures and
operating system crashes) and transaction failures.
? Atomicity,consistency,isolation, durability
? Concurrency-control manager controls the interaction
among the concurrent transactions,to ensure the
consistency of the database.
? Failure recovery
?Silberschatz,Korth and Sudarshan1.23Database System Concepts
8 Database System Structure
? Storage Manager
? Storage manager is a program module that
provides the interface between the low-level
data stored in the database and the application
programs and queries submitted to the system.
? The storage manager components include,
?Authorization and integrity manager
?Transaction manager
?File manager
?Buffer manager
? Data files,Data dictionary,Indices
?Silberschatz,Korth and Sudarshan1.24Database System Concepts
8 Database System Structure (Cont.)
? The Query Processor
? DDL interpreter
? DML compiler
? Query evaluation engine
?Silberschatz,Korth and Sudarshan1.25Database System Concepts
Overall System Structure
?Silberschatz,Korth and Sudarshan1.26Database System Concepts
9 Application Architectures
?Two-tier architecture,E.g,client programs using
ODBC/JDBC to communicate with a database
?Three-tier architecture,E.g,web-based applications,and
applications built using,middleware”
?Silberschatz,Korth and Sudarshan1.27Database System Concepts
10 History of Database Systems
? 1950s and 1960s
? Late 1960s and 1970s
? 1980s
? Early 1990s
? Late 1990s
DATABASE SYSTEM
CONCEPTS
instructor,Jingsheng Lei(雷景生 )
E-mail,jshlei@hainu.edu.cn
?Silberschatz,Korth and Sudarshan1.2Database System Concepts
Chapter 1,Introduction
? Applications of Database Systems
? Database Systems versus File Systems
? View of Data
? Data Models
? Database Language
? Database Users and Administrator
? Transaction Management
? Database System Structure
? Application Architectures
? History of Database Systems
? Summary
?Silberschatz,Korth and Sudarshan1.3Database System Concepts
Database Management System (DBMS)
? Collection of interrelated data.
? Set of programs to access the data,
? DB contains information about a particular enterprise.
? DBMS provides an environment that is both convenient
and efficient to use.
? Database systems are designed to manage large bodies
of information.
? DBS must ensure the safety of the information stored.
? Several users.
Data Database(DB) Database Management System
(DBMS) Database System(DBS)
?Silberschatz,Korth and Sudarshan1.4Database System Concepts
1 Applications of Database Systems
? Database Applications:
? Banking,all transactions
? Airlines,reservations,schedules
? Universities,registration,grades
? Sales,customers,products,purchases
? Manufacturing,production,inventory,orders,
supply chain
? Human resources,employee records,salaries,
tax deductions
? Databases touch all aspects of our lives
?Silberschatz,Korth and Sudarshan1.5Database System Concepts
2 Database Systems versus File Systems
In the early days,database applications were built on top of
file systems
? Drawbacks of using file systems to store data:
? Data redundancy and inconsistency
?Multiple file formats,duplication of information in different files
? Difficulty in accessing data
?Need to write a new program to carry out each new task
? Data isolation —multiple files and formats
? Integrity problems
?Integrity constraints (e.g,account balance > 0) become part of
program code
?Hard to add new constraints or change existing ones
?Silberschatz,Korth and Sudarshan1.6Database System Concepts
2 Database Systems versus File
Systems(Cont.)
? Drawbacks of using file systems (cont.)
? Atomicity of updates
?Failures may leave database in an inconsistent
state with partial updates carried out
?E.g,transfer of funds from one account to
another should either complete or not happen at
all
? Concurrent access by multiple users
?Concurrent accessed needed for performance
?Uncontrolled concurrent accesses can lead to
inconsistencies
–E.g,two people reading a balance and
updating it at the same time
? Security problems
?Silberschatz,Korth and Sudarshan1.7Database System Concepts
3 View of Data
3.1 Data Abstraction
? Physical level describes how a record (e.g.,customer) is
stored.
? Logical level,describes data stored in database,and the
relationships among the data.
type customer = record
name, string;
street, string;
city, integer;
end;
? View level,application programs hide details of data
types,Views can also hide information (e.g.,salary) for
security purposes,
?Silberschatz,Korth and Sudarshan1.8Database System Concepts
3 View of Data (Cont.)
An architecture for a database system
?Silberschatz,Korth and Sudarshan1.9Database System Concepts
3 View of Data (Cont.)
3.2 Instances and Schemas
? Similar to types and variables in programming
languages
? Schema – the logical structure of the database
? e.g.,the database consists of information about a
set of customers and accounts and the
relationship between them)
? Analogous to type information of a variable in a
program
? Physical schema,database design at the
physical level
? Logical schema,database design at the logical
level
?Silberschatz,Korth and Sudarshan1.10Database System Concepts
3 View of Data (Cont.)
? Instance – the actual content of the database at a
particular point in time
? Analogous to the value of a variable
? Physical Data Independence – the ability to
modify the physical schema without changing the
logical schema
? Applications depend on the logical schema
? In general,the interfaces between the various
levels and components should be well defined
so that changes in some parts do not seriously
influence others.
?Silberschatz,Korth and Sudarshan1.11Database System Concepts
4 Data Models
? A collection of tools for describing
? data
? data relationships
? data semantics
? data constraints
? Entity-Relationship model
? Relational model
? Other models,
? object-oriented model,object-relational data
model
? semi-structured data models
? Older models,network model and hierarchical model
?Silberschatz,Korth and Sudarshan1.12Database System Concepts
4.1 Entity-Relationship Model
Example of schema in the entity-relationship model
?Silberschatz,Korth and Sudarshan1.13Database System Concepts
4.1 Entity Relationship Model (Cont.)
? E-R model of real world
? Entities (objects)
?E.g,customers,accounts,bank branch
? Relationships between entities
?E.g,Account A-101 is held by customer Johnson
?Relationship set depositor associates customers
with accounts
? Widely used for database design
? Database design in E-R model usually converted to
design in the relational model (coming up next)
which is used for storage and processing
?Silberschatz,Korth and Sudarshan1.14Database System Concepts
4.2 Relational Model
? Example of tabular data in the relational model
customer-
nameCustomer-id
customer-
street
customer-
city
account-
number
Johnson
Smith
Johnson
Jones
Smith
192-83-7465
019-28-3746
192-83-7465
321-12-3123
019-28-3746
Alma
North
Alma
Main
North
Palo Alto
Rye
Palo Alto
Harrison
Rye
A-101
A-215
A-201
A-217
A-201
Attributes
?Silberschatz,Korth and Sudarshan1.15Database System Concepts
A Sample Relational Database
?Silberschatz,Korth and Sudarshan1.16Database System Concepts
5 Database Language
? 5.1 Data Definition Language (DDL)
? Specification notation for defining the database schema
?E.g,
create table account (
account-number char(10),
balance integer)
? DDL compiler generates a set of tables stored in a data
dictionary
? Data dictionary contains metadata (i.e.,data about data)
? database schema
?Data storage and definition language
– language in which the storage structure and
access methods used by the database system
are specified
–Usually an extension of the data definition
language
?Silberschatz,Korth and Sudarshan1.17Database System Concepts
5 Database Language (Cont.)
? 5.2 Data Manipulation Language (DML)
? Language for accessing and manipulating the data
organized by the appropriate data model
? Two classes of languages
?Procedural – user specifies what data is required
and how to get those data
?Nonprocedural – user specifies what data is
required without specifying how to get those data
? SQL is the most widely used query language
?Silberschatz,Korth and Sudarshan1.18Database System Concepts
5 Database Language (Cont.)
? 5.3 SQL
? SQL,widely used non-procedural language
?E.g,find the name of the customer with customer-
id 192-83-7465
select customer.customer-name
from customer
where customer.customer-id = ?192-83-
7465?
?E.g,find the balances of all accounts held by the
customer with customer-id 192-83-7465
select account.balance
from depositor,account
where depositor.customer-id = ?192-83-
7465? and depositor.account-number =
account.account-number
?Silberschatz,Korth and Sudarshan1.19Database System Concepts
5 Database Language (Cont.)
? Application programs generally access databases
through one of
? Language extensions to allow embedded SQL
? Application program interface (e.g,
ODBC/JDBC) which allow SQL queries to be
sent to a database
?Silberschatz,Korth and Sudarshan1.20Database System Concepts
6 Database Users AND Database
Administrator
? Database Users
? Application programmers – interact with system
through DML calls
? Sophisticated users – form requests in a database
query language
? Specialized users – write specialized database
applications that do not fit into the traditional data
processing framework
? Naive users – invoke one of the permanent
application programs that have been written
previously
?E.g,people accessing database over the web,
bank tellers,clerical staff
?Silberschatz,Korth and Sudarshan1.21Database System Concepts
6 Database Users AND Database
Administrator (Cont.)
? Database administrator's duties include:
? Schema definition
? Storage structure and access method definition
? Schema and physical organization modification
? Granting user authority to access the database
? Routine maintenance
?Silberschatz,Korth and Sudarshan1.22Database System Concepts
7 Transaction Management
? A transaction is a collection of operations that
performs a single logical function in a database
application
? Transaction-management component ensures that the
database remains in a consistent (correct) state
despite system failures (e.g.,power failures and
operating system crashes) and transaction failures.
? Atomicity,consistency,isolation, durability
? Concurrency-control manager controls the interaction
among the concurrent transactions,to ensure the
consistency of the database.
? Failure recovery
?Silberschatz,Korth and Sudarshan1.23Database System Concepts
8 Database System Structure
? Storage Manager
? Storage manager is a program module that
provides the interface between the low-level
data stored in the database and the application
programs and queries submitted to the system.
? The storage manager components include,
?Authorization and integrity manager
?Transaction manager
?File manager
?Buffer manager
? Data files,Data dictionary,Indices
?Silberschatz,Korth and Sudarshan1.24Database System Concepts
8 Database System Structure (Cont.)
? The Query Processor
? DDL interpreter
? DML compiler
? Query evaluation engine
?Silberschatz,Korth and Sudarshan1.25Database System Concepts
Overall System Structure
?Silberschatz,Korth and Sudarshan1.26Database System Concepts
9 Application Architectures
?Two-tier architecture,E.g,client programs using
ODBC/JDBC to communicate with a database
?Three-tier architecture,E.g,web-based applications,and
applications built using,middleware”
?Silberschatz,Korth and Sudarshan1.27Database System Concepts
10 History of Database Systems
? 1950s and 1960s
? Late 1960s and 1970s
? 1980s
? Early 1990s
? Late 1990s
