ITP 140 Mobile Technologies. Databases Client/Server

Transcription

1 ITP 140 Mobile Technologies Databases Client/Server

2 Databases Data: recorded facts and figures Information: knowledge derived from data Databases record data, but they do so in such a way that we can produce information from the data Example: The data on STUDENTs, CLASSes and GRADEs could produce information about each student s GPA 2

3 Introducing the database Database: shared, integrated computer structure that stores a collection of: End-user data: raw facts of interest to the end user Metadata: data about data Provides description of data characteristics and relationships in data Complements and expands the value of data Database management system (DBMS): Manages structure and controls access to data 3

4 The database A database is a self-describing collection of integrated tables The tables are called integrated because they store data about the relationships between rows of data A database is called self-describing because it stores a description of itself The self-describing data is called metadata, which is data about data 4

5 The characteristics of databases The purpose of a database is to help people track things of interest Data is stored in tables, which have rows and columns like a spreadsheet. A database may have multiple tables where each table stores data about a different thing Each row in a table stores data about an occurrence or instance of the thing of interest A database stores data and relationships 5

6 Role and advantages of the DBMS DBMS is the intermediary between the user and the database Database structure stored as a file collection Can only access files through DBMS DBMS enables data to be shared DBMS integrates many users views of the data 6

7 Role and advantages of the DBMS 7

8 Role and advantages of the DBMS Advantages of a DBMS: Improved data sharing Improved data security Better data integration Minimized data inconsistency Improved data access Improved decision making Increased end-user productivity 8

9 Types of Databases Databases can be classified by: Number of users Database location(s) Expected type and extent of use Single-user database supports only one user at a time Desktop database: single-user; runs on PC Multiuser database supports multiple users at the same time Workgroup and enterprise databases 9

10 Types of databases Centralized database: data located at a single site Distributed database: data distributed across several different sites Operational database: supports a company s day-to-day operations Transactional or production database Data warehouse: stores data used for tactical or strategic decisions Analytical database 10

11 Database system environment Database system: defines and regulates the collection, storage, management, use of data Major parts of database system 1. Hardware 2. Software 3. People 4. Procedures 5. Data 11

12 Database system environment 12

13 Database system environment Hardware: all the system s physical devices Software: 3 types of software required: 1. Operating system software 2. DBMS software 3. Application programs and utility software 13

14 Database system environment People: all users of the database system System and database administrators Database designers System analysts and programmers End users Procedures: instructions and rules that govern the design and use of the database system Data: the collection of facts stored in the database 14

15 Database system 15

16 DBMS functions Data dictionary management DBMS stores definitions of data elements and relationships (metadata) in a data dictionary DBMS looks up required data component structures and relationships Changes automatically recorded in dictionary 16

17 Typical metadata tables 17

18 Metadata in Microsoft SQL Server 18

19 DBMS functions Data storage management DBMS create and manage complex structures required for data storage Also store related data entry forms, screen definitions, report definitions, etc. Performance tuning: activities that make the database perform more efficiently DBMS may store database in multiple physical files 19

20 Metadata in Oracle 20

21 DBMS functions Data transformation and presentation DBMS transforms data entered to conform to required data structures DBMS transforms physically retrieved data to conform to user s logical expectations Security management DBMS creates a security system that enforces user security and data privacy Security rules determine which users may access the database, which items may be accessed, etc. 21

22 DBMS functions Multiuser access control DBMS uses sophisticated algorithms to ensure concurrent access does not compromise integrity Backup and recovery management DBMS provides backup and data recovery to ensure data safety and integrity Recovery management deals with recovery of database after a failure Critical to preserving database s integrity 22

23 DBMS functions Data integrity management DBMS promotes and enforces integrity rules Minimizes redundancy Maximizes consistency Data relationships stored in data dictionary used to enforce data integrity Integrity especially important in transactionoriented database systems 23

24 DBMS functions Database access languages and application programming interfaces DBMS provides access through a query system Structured Query Language (SQL) is the de facto query language Standard supported by majority of DBMS vendors 24

25 DBMS functions Database communication interfaces Current DBMSs accept end-user requests via multiple (and different) network environments Can occur in the following ways: End users generate answers to queries by filling in screen forms through a Web browser DBMS automatically publishes predefined reports on a Web site DBMS connects to third-party systems to distribute information via 25

26 Database applications Applications are the computer programs users interact with and can include: Create and process forms Process user queries Create and process reports Execute application logic Control applications 26

27 Components of a DB system with SQL 27

28 Database applications: forms 28

29 Database applications: queries SELECT LastName, FirstName, Address FROM STUDENT WHERE StudentNumber > 2; 29

30 Database applications: reports 30

31 Prominent DBMS products Microsoft Access Microsoft SQL Server sql-server/ Oracle Database MySQL IBM DB2 SAP HANA 31

32 Client / server system A networked computing model Computation is distributed between clients and servers Client A computer (or other networked device) that requests and uses a service Server A computer (PC/mainframe) that provides a service 32

33 Application logic breakdown Presentation logic Input (keyboard / mouse) Output monitor/printer Processing logic I/O processing Business rules Data management Storage logic Data storage & retrieval GUI Interface Procedures, functions and programs DBMS activities 33

34 Client / Server architectures File server architecture Client does extensive processing Database server architecture Three-tier architecture Client does little processing 34

35 File server architecture Processing occurs at the requesting computer Entire files are transferred from server to client Pros: Requires minimal infrastructure (hardware, software) Cons: Requires high bandwidth network Each client maintains full DBMS Requires robust clients and distributed DBMS 35

36 File server architecture FAT / THICK / RICH CLIENT 36

37 Database server architecture Sometimes called two-tier Client s role I/O processing logic Some business rules Server s role Data storage and access control DBMS is on server ONLY 37

38 Two-tier architecture pros / cons Pros Reduced requirements for clients Reduced network traffic Improved data integrity (from centralized DBMS) Cons DBMS can perform stored procedures Diffusion of business rules & application logic 38

39 Tangent: stored procedures Are compiled (series of) SQL statements Can be invoked instead remotely Instead of having clients direct multi-part queries Advantages: Reduced network traffic Improved security Improved data integrity Thinner clients 39

40 Two-tier database server architecture Thinner clients DBMS only on server 40

41 Three tier architectures Client GUI interface (I/O processing) Browser Application server Business rules Web server Database server Data storage DBMS Thin Client Client used only for user interface and I/O processing limited data storage 41

42 About three-tier architectures Advantages Scalability & flexibility Long-term cost reduction Better match of systems to business needs Competitive advantage Reduced risk Staged delivery of functionality speeds deployment Reduced network traffic due to increased processing at data source Facilitation of Web-enabled applications 42

43 Three-tier architecture Thinnest clients Business rules on separate server DBMS only on DB server 43

44 Two tier logic distribution Logic can be processed at client, server or both 44

45 n-tier client-server environment Logic processed at application (or web) server 45

46 Middleware Software (usually an API) that allows an application to interoperate with other software No need for programmer / user to understand internal processing The glue that holds client / server applications Example uses: Asynchronous communication (push, remote procedures) Data storage (to cloud and various media) User interfaces (hardware, software) 46

47 Database middleware ODBC Open Database Connectivity Windows based Supported by most DB vendors OLE-DB Object Linking and Embedding, Database Microsoft enhancement on ODBC JDBC Java Database Connectivity Special Java classes to allow Java code to use databases 47

48 ODBC architecture Client does not need to know anything about the DBMS Application Program Interface (API) provides common interface to all DBMSs Each DBMS has its own ODBC-compliant driver 48

49 Web-to-database middleware 49

50 Web based database applications Why web-based? Web browsers are simple to use Information transfer can take place across different platforms Development time and cost have been reduced Sites can be static (no database) or dynamic/ interactive (with database) Potential e-business advantages (improved customer service, faster market time, better supply chain management) 50

51 Database backed internet/intranet app 51

52 Components for dynamic websites DBMS: Oracle, Microsoft SQL Server, MySQL Web server: Apache, Microsoft IIS, Nginx Server-side tech:.net, PHP, Python, Java Web browser: Internet Exploder, Firefox, Safari, Chrome, Opera 52