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Chapter 1: Introduction Hankz Hankui Zhuo (卓汉逵) Email: [email protected] Homepage: http://www.zsusoft.com/~hankz Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz How to get good marks? • Marks = regular (40%) + final exam (60%) Roll calls (20%) Assignments (20%) Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 2 Syllabus • • • • • • • • • • Chapter 1: Introduction Chapter 2: Introduction to the Relational Model Chapter 3: Introduction to SQL Chapter 6: Database Design and EntityRelationship Model Chapter 7: Relational Database Design Chapter 11: Storage and File Structure Chapter 12: Indexing and Hashing. Chapter 13: Query Processing Chapter 15: Transactions *Chapter 20: Data Warehousing and Mining Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 3 Database Management System (DBMS) • Describe a particular enterprise: – A collection of interrelated data – Programs – Environment Environment Programs DBMS data Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 4 Database Applications • Banking Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 5 Database Applications • Banking • Airlines Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 6 Database Applications • Banking • Airlines • Universities Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 7 Database Applications • • • • Banking Airlines Universities Sales Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 8 Database Applications • • • • • • • • Banking Airlines Universities Sales Online retailers Manufacturing Human resources … Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 9 Purpose • In the early days, applications were built directly on top of file systems • Drawbacks : – 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 10 Purpose – 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 ones – 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 11 Purpose – 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 – Security problems • Hard to provide user access to some, but not all, data • Purpose of database systems? – offer solutions to all the above problems!!!! Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 12 Architecture of database systems Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 13 Architecture of database systems • 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 customer_id : string; customer_name : string; customer_street : string; customer_city : integer; end; • View level: application programs hide details of data types. Views can also hide information (such as an employee’s salary) for security purposes. Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 14 Schemas • the logical structure of the database – Example: 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 15 Instances • the actual content of the database at a particular point in time – Analogous to the value of a variable Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 16 Instances • the actual content of the database at a particular point in time – Analogous to the value of a variable Independence between schemas and instance? Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 17 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. Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 18 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. Nice! But, do we have any tool to model the data? Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 19 Tools • Relational model • Entity-Relationship data model (mainly for database design) • Object-based data models (Object-oriented and Object-relational) • Semistructured data model (XML) • Other older models: – Network model – Hierarchical model Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 20 Relational Model As an example, Relational Model: Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz Attributes 21 A Sample Relational Database Many tables “stacked” together form a database! Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 22 A Sample Relational Database Many tables “stacked” together form a database! Having “data” is not enough. We also need Data Manipulation Language (DML). Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 23 Data Manipulation Language (DML) • Language for accessing and manipulating the data organized by the appropriate data model – DML also known as query language Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 24 Data Manipulation Language (DML) • Language for accessing and manipulating the data organized by the appropriate data model – DML also known as query language • Two classes of languages – Procedural – user specifies what data is required and how to get those data – Declarative (nonprocedural) – user specifies what data is required without specifying how to get those data • SQL is the widely used nonprocedural language Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 25 SQL • SQL: widely used non-procedural language – 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’ Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 26 SQL • SQL: widely used non-procedural language – 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’ – 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 27 SQL • SQL: widely used non-procedural language – Example: the name of the customer with We now Find know: customer-id 192-83-7465 select customer.customer_name Data DML from customer (database) (SQL) where customer.customer_id = ‘192-83-7465’ + – 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 28 SQL • SQL: widely used non-procedural language – Example: the name of the customer with We now Find know: customer-id 192-83-7465 select customer.customer_name Data DML from customer (database) (SQL) where customer.customer_id = ‘192-83-7465’ + – Example: Find the balances of all accounts held by Enough? Something missing? 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 29 SQL • SQL: widely used non-procedural language – Example: the name of the customer with We now Find know: customer-id 192-83-7465 select customer.customer_name Data DML from customer (database) (SQL) where customer.customer_id = ‘192-83-7465’ + – Example: Find the balances of all accounts held by Enough? Something missing? Yes! 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 Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 30 SQL • SQL: widely used non-procedural language – Example: the name of the customer with We now Find know: customer-id 192-83-7465 select customer.customer_name Data DML from customer (database) (SQL) where customer.customer_id = ‘192-83-7465’ + – Example: Find the balances of all accounts held by How ? the customer with customer-id 192-83-7465 select account.balance from depositor, account Design where depositor.customer_id = ‘192-83-7465’ and depositor.account_number = account.account_number Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 31 Database Design The process of designing the general structure of the database: – Logical Design – Deciding on the database schema. • Business decision – What attributes should we record in the database? • Computer Science decision – What relation schemas should we have and how should the attributes be distributed among the various relation schemas? – Physical Design – Deciding on the physical layout of the database Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 32 Database Design The process of designing the general structure of the database: – Logical Design – Deciding on the database schema. An–example method:should we record in • Business decision What attributes the database? Entity-relationship model • Computer Science decision – What relation schemas should we have and how should the attributes be distributed among the various relation schemas? – Physical Design – Deciding on the physical layout of the database Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 33 Database Design The process of designing the general structure of the database: – Logical Design – Deciding on the database schema. An–example method:should we record in • Business decision What attributes the database? Entity-relationship model • Computer Science decision – What relation schemas should we have and how should the attributes be distributed among the various relation schemas? – Physical Design – Deciding on the physical layout of the database Storage Management Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 34 The Entity-Relationship Model • Models an enterprise as a collection of entities and relationships – Entity: a “thing” or “object” in the enterprise that is distinguishable from other objects • Described by a set of attributes – Relationship: an association among several entities • Represented diagrammatically by an entityrelationship diagram: Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 35 Storage Management • 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 is responsible to the following tasks: – Interaction with the file manager – Efficient storing, retrieving and updating of data • Issues: – Storage access – File organization – Indexing and hashing Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 36 SQL • SQL: widely used non-procedural language – Example: the name of the customer with We now Find know: customer-id 192-83-7465 select customer.customer_name Data DML from customer (database) (SQL) where customer.customer_id = ‘192-83-7465’ + – Example: Find the balances of all accounts held by the customer with customer-id 192-83-7465 select account.balance from depositor, account Design where depositor.customer_id = ‘192-83-7465’ and depositor.account_number = account.account_number Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 37 SQL • SQL: widely used non-procedural language – Example: the name of the customer with We now Find know: customer-id 192-83-7465 select customer.customer_name Data DML from customer (database) (SQL) where customer.customer_id = ‘192-83-7465’ + – Example: Find the balances of all accounts held by the customer with customer-id 192-83-7465 select account.balance Query from depositor, account Design Processing and where depositor.customer_id = ‘192-83-7465’ depositor.account_number = account.account_number Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 38 Query Processing 1.Parsing and translation 2.Optimization 3.Evaluation Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 39 Query Processing 1.Parsing and translation 2.Optimization 3.Evaluation In query processing, one of the most important concepts : transaction Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 40 Transaction Management • A transaction is a collection of operations • 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. • Concurrency-control manager controls the interaction among the concurrent transactions, to ensure the consistency of the database. Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 41 Finally, let me say something about the whole database architecture! Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 42 Database Architecture The architecture of a database systems is greatly influenced by the underlying computer system on which the database is running: – Centralized – Client-server – Parallel (multi-processor) – Distributed Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 43 Database Administrator • Coordinates all the activities of the database system. • Database administrator's duties include: – – – – – – – Schema definition Storage structure and access method definition Schema and physical organization modification Granting user authority Specifying integrity constraints Acting as liaison with users Monitoring performance and responding to changes Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 44 History of Database Systems • 1950s and early 1960s: – Data processing using magnetic tapes for storage • Tapes provide only sequential access – Punched cards for input • Late 1960s and 1970s: – Hard disks allow direct access to data – Network and hierarchical data models in widespread use – 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 – High-performance (for the era) transaction processing Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 45 History of Database Systems • 1980s: – Research relational prototypes evolve into commercial systems • SQL becomes industrial standard – Parallel and distributed database systems – Object-oriented database systems • 1990s: – Large decision support and data-mining applications – Large multi-terabyte data warehouses – Emergence of Web commerce • 2000s: – XML and XQuery standards – Automated database administration Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 46 • For students interested in database research: – Top conferences: • • • • VLDB Sigmod Sigkdd ICDE You can find papers via google with “<conference name>+year”, e.g., “VLDB 2011”. Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 47 • For students interested in database research: – Top conferences: • • • • VLDB Sigmod Sigkdd ICDE – Top journals: • • • • ACM Transactions on Database Systems VLDB Journal ACM Transactions on Information and Systems IEEE Transactions on Knowledge and Data Engineering Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 48 The End! Hankz Hankui Zhuo: http://www.zsusoft.com/~hankz 49