Your SlideShare is downloading. ×
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Introduction To DBMS
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Introduction To DBMS

1,015

Published on

Chapter 1 …

Chapter 1
Database Concepts
Korth

Published in: Education, Technology
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
1,015
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
93
Comments
0
Likes
1
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Chapter 1: Introduction Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See www.db-book.com for conditions on re-use
  • 2. Chapter 1: Introduction s Purpose of Database Systems s Database Languages s Relational Databases s Database Design s Data Models s Database Internals s Database Users and Administrators s Overall Structure s History of Database Systemsatabase System Concepts - 5 th Edition, May 23, 2005 1.2 ©Silberschatz, Korth and Sudarshan
  • 3. Database Management System (DBMS) s DBMS contains information about a particular enterprise q Collection of interrelated data q Set of programs to access the data q An environment that is both convenient and efficient to use s Database Applications: q Banking: all transactions q Airlines: reservations, schedules q Universities: registration, grades q Sales: customers, products, purchases q Online retailers: order tracking, customized recommendations q Manufacturing: production, inventory, orders, supply chain q Human resources: employee records, salaries, tax deductions s Databases touch all aspects of our livesatabase System Concepts - 5 th Edition, May 23, 2005 1.3 ©Silberschatz, Korth and Sudarshan
  • 4. Purpose of Database Systems s In the early days, database applications were built directly on top of file systems s Drawbacks of using file systems to store data: q Data redundancy and inconsistency  Multiple file formats, duplication of information in different files q Difficulty in accessing data  Need to write a new program to carry out each new task q Data isolation — multiple files and formats q Integrity problems  Integrity constraints (e.g. account balance > 0) become “buried” in program code rather than being stated explicitly  Hard to add new constraints or change existing onesatabase System Concepts - 5 th Edition, May 23, 2005 1.4 ©Silberschatz, Korth and Sudarshan
  • 5. Purpose of Database Systems (Cont.) s Drawbacks of using file systems (cont.) q Atomicity of updates  Failures may leave database in an inconsistent state with partial updates carried out  Example: Transfer of funds from one account to another should either complete or not happen at all q Concurrent access by multiple users  Concurrent accessed needed for performance  Uncontrolled concurrent accesses can lead to inconsistencies – Example: Two people reading a balance and updating it at the same time q Security problems  Hard to provide user access to some, but not all, data s Database systems offer solutions to all the above problemsatabase System Concepts - 5 th Edition, May 23, 2005 1.5 ©Silberschatz, Korth and Sudarshan
  • 6. Levels of Abstraction s Physical level: describes how a record (e.g., customer) is stored. s Logical level: describes data stored in database, and the relationships among the data. type customer = record customer_id : string; customer_name : string; customer_street : string; customer_city : string; end; s View level: application programs hide details of data types. Views can also hide information (such as an employee’s salary) for security purposes.atabase System Concepts - 5 th Edition, May 23, 2005 1.6 ©Silberschatz, Korth and Sudarshan
  • 7. View of Data An architecture for a database systematabase System Concepts - 5 th Edition, May 23, 2005 1.7 ©Silberschatz, Korth and Sudarshan
  • 8. Instances and Schemas s Similar to types and variables in programming languages s Schema – the logical structure of the database q Example: The database consists of information about a set of customers and accounts and the relationship between them) q Analogous to type information of a variable in a program q Physical schema: database design at the physical level q Logical schema: database design at the logical level s Instance – the actual content of the database at a particular point in time q Analogous to the value of a variable s Physical Data Independence – the ability to modify the physical schema without changing the logical schema q Applications depend on the logical schema q 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.atabase System Concepts - 5 th Edition, May 23, 2005 1.8 ©Silberschatz, Korth and Sudarshan
  • 9. Data Models s A collection of tools for describing q Data q Data relationships q Data semantics q Data constraints s Relational model s Entity-Relationship data model (mainly for database design) s Object-based data models (Object-oriented and Object-relational) s Semistructured data model (XML) s Other older models: q Network model q Hierarchical modelatabase System Concepts - 5 th Edition, May 23, 2005 1.9 ©Silberschatz, Korth and Sudarshan
  • 10. Data Manipulation Language (DML) s Language for accessing and manipulating the data organized by the appropriate data model q DML also known as query language s Two classes of languages q Procedural – user specifies what data is required and how to get those data q Declarative (nonprocedural) – user specifies what data is required without specifying how to get those data s SQL is the most widely used query languageatabase System Concepts - 5 th Edition, May 23, 2005 1.10 ©Silberschatz, Korth and Sudarshan
  • 11. Data Definition Language (DDL) s Specification notation for defining the database schema Example: create table account ( account_number char(10), branch_name char(10), balance integer) s DDL compiler generates a set of tables stored in a data dictionary s Data dictionary contains metadata (i.e., data about data) q Database schema q Data storage and definition language  Specifies the storage structure and access methods used q Integrity constraints  Domain constraints  Referential integrity (e.g. branch_name must correspond to a valid branch in the branch table) q Authorizationatabase System Concepts - 5 th Edition, May 23, 2005 1.11 ©Silberschatz, Korth and Sudarshan
  • 12. Relational Model Attributes s Example of tabular data in the relational modelatabase System Concepts - 5 th Edition, May 23, 2005 1.12 ©Silberschatz, Korth and Sudarshan
  • 13. A Sample Relational Databaseatabase System Concepts - 5 th Edition, May 23, 2005 1.13 ©Silberschatz, Korth and Sudarshan
  • 14. SQL s SQL: widely used non-procedural language q Example: 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’ q Example: 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 s Application programs generally access databases through one of q Language extensions to allow embedded SQL q Application program interface (e.g., ODBC/JDBC) which allow SQL queries to be sent to a databaseatabase System Concepts - 5 th Edition, May 23, 2005 1.14 ©Silberschatz, Korth and Sudarshan
  • 15. Database Design The process of designing the general structure of the database: s Logical Design – Deciding on the database schema. Database design requires that we find a “good” collection of relation schemas. q Business decision – What attributes should we record in the database? q Computer Science decision – What relation schemas should we have and how should the attributes be distributed among the various relation schemas? s Physical Design – Deciding on the physical layout of the databaseatabase System Concepts - 5 th Edition, May 23, 2005 1.15 ©Silberschatz, Korth and Sudarshan
  • 16. The Entity-Relationship Model s Models an enterprise as a collection of entities and relationships q Entity: a “thing” or “object” in the enterprise that is distinguishable from other objects  Described by a set of attributes q Relationship: an association among several entities s Represented diagrammatically by an entity-relationship diagram:atabase System Concepts - 5 th Edition, May 23, 2005 1.16 ©Silberschatz, Korth and Sudarshan
  • 17. Other Data Models s Object-oriented data model s Object-relational data modelatabase System Concepts - 5 th Edition, May 23, 2005 1.17 ©Silberschatz, Korth and Sudarshan
  • 18. Database Application Architectures (web browser) Old Modernatabase System Concepts - 5 th Edition, May 23, 2005 1.18 ©Silberschatz, Korth and Sudarshan
  • 19. Database Management System Internals s Storage management s Query processing s Transaction processingatabase System Concepts - 5 th Edition, May 23, 2005 1.19 ©Silberschatz, Korth and Sudarshan
  • 20. Storage Management s 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. s The storage manager is responsible to the following tasks: q Interaction with the file manager q Efficient storing, retrieving and updating of data s Issues: q Storage access q File organization q Indexing and hashingatabase System Concepts - 5 th Edition, May 23, 2005 1.20 ©Silberschatz, Korth and Sudarshan
  • 21. Query Processing 1. Parsing and translation 2. Optimization 3. Evaluationatabase System Concepts - 5 th Edition, May 23, 2005 1.21 ©Silberschatz, Korth and Sudarshan
  • 22. Query Processing (Cont.) s Alternative ways of evaluating a given query q Equivalent expressions q Different algorithms for each operation s Cost difference between a good and a bad way of evaluating a query can be enormous s Need to estimate the cost of operations q Depends critically on statistical information about relations which the database must maintain q Need to estimate statistics for intermediate results to compute cost of complex expressionsatabase System Concepts - 5 th Edition, May 23, 2005 1.22 ©Silberschatz, Korth and Sudarshan
  • 23. Transaction Management s A transaction is a collection of operations that performs a single logical function in a database application s 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. s Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database.atabase System Concepts - 5 th Edition, May 23, 2005 1.23 ©Silberschatz, Korth and Sudarshan
  • 24. Overall System Structureatabase System Concepts - 5 th Edition, May 23, 2005 1.24 ©Silberschatz, Korth and Sudarshan
  • 25. History of Database Systems s 1950s and early 1960s: q Data processing using magnetic tapes for storage  Tapes provide only sequential access q Punched cards for input s Late 1960s and 1970s: q Hard disks allow direct access to data q Network and hierarchical data models in widespread use q Ted Codd defines the relational data model  Would win the ACM Turing Award for this work  IBM Research begins System R prototype  UC Berkeley begins Ingres prototype q High-performance (for the era) transaction processingatabase System Concepts - 5 th Edition, May 23, 2005 1.25 ©Silberschatz, Korth and Sudarshan
  • 26. History (cont.) s 1980s: q Research relational prototypes evolve into commercial systems  SQL becomes industry standard q Parallel and distributed database systems q Object-oriented database systems s 1990s: q Large decision support and data-mining applications q Large multi-terabyte data warehouses q Emergence of Web commerce s 2000s: q XML and XQuery standards q Automated database administration q Increasing use of highly parallel database systems q Web-scale distributed data storage systemsatabase System Concepts - 5 th Edition, May 23, 2005 1.26 ©Silberschatz, Korth and Sudarshan
  • 27. End of Chapter 1Database System Concepts, 5th Ed. ©Silberschatz, Korth and SudarshanSee www.db-book.com for conditions on re-use
  • 28. Database Users Users are differentiated by the way they expect to interact with the system s Application programmers – interact with system through DML calls s Sophisticated users – form requests in a database query language s Specialized users – write specialized database applications that do not fit into the traditional data processing framework s Naï ve users – invoke one of the permanent application programs that have been written previously q Examples, people accessing database over the web, bank tellers, clerical staffatabase System Concepts - 5 th Edition, May 23, 2005 1.28 ©Silberschatz, Korth and Sudarshan
  • 29. Database Administrator s Coordinates all the activities of the database system q has a good understanding of the enterprise’s information resources and needs. s Database administrators duties include: q Storage structure and access method definition q Schema and physical organization modification q Granting users authority to access the database q Backing up data q Monitoring performance and responding to changes  Database tuningatabase System Concepts - 5 th Edition, May 23, 2005 1.29 ©Silberschatz, Korth and Sudarshan
  • 30. Database Architecture The architecture of a database systems is greatly influenced by the underlying computer system on which the database is running: s Centralized s Client-server s Parallel (multiple processors and disks) s Distributedatabase System Concepts - 5 th Edition, May 23, 2005 1.30 ©Silberschatz, Korth and Sudarshan
  • 31. Object-Relational Data Models s Extend the relational data model by including object orientation and constructs to deal with added data types. s Allow attributes of tuples to have complex types, including non-atomic values such as nested relations. s Preserve relational foundations, in particular the declarative access to data, while extending modeling power. s Provide upward compatibility with existing relational languages.atabase System Concepts - 5 th Edition, May 23, 2005 1.31 ©Silberschatz, Korth and Sudarshan
  • 32. XML: Extensible Markup Language s Defined by the WWW Consortium (W3C) s Originally intended as a document markup language not a database language s The ability to specify new tags, and to create nested tag structures made XML a great way to exchange data, not just documents s XML has become the basis for all new generation data interchange formats. s A wide variety of tools is available for parsing, browsing and querying XML documents/dataatabase System Concepts - 5 th Edition, May 23, 2005 1.32 ©Silberschatz, Korth and Sudarshan
  • 33. Figure 1.4atabase System Concepts - 5 th Edition, May 23, 2005 1.33 ©Silberschatz, Korth and Sudarshan
  • 34. Figure 1.7atabase System Concepts - 5 th Edition, May 23, 2005 1.34 ©Silberschatz, Korth and Sudarshan

×