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Premium member Presentation Transcript Unit 1 Introduction to DBMS (Database Management Systems) : 1-1 Unit 1 Introduction to DBMS (Database Management Systems) Outline of Unit 1 : 1-2 Outline of Unit 1 1.1 Information Systems 1.2 An Overview of a Database System 1.3 An Architecture for a Database System 1.4 Database Technology Trends 1.1 Information Systems : 1-3 1.1 Information Systems Stages of Information System : 1-4 Stages of Information System Stage 0: Manual Information System Records Files Index Cards Stage 1: Sequential Information Systems Tapes Files slow, non-interactive, redundancy,... . Stage 2: File Based Information Systems Disk (direct access) application program has its own file data dependence data redundancy Stage 3: DBMS based Information Systems Generalized data management software Transaction processing Slide 5: 1-5 DBMS based Information Systems: Basic Approach - Integration : 1-6 DBMS based Information Systems: Basic Approach - Integration (1) Integration of Information Description of the integrated view of data is the "Conceptual Schema" of the database DBMS based Information Systems: Basic Approach – Simple views and High level language : 1-7 DBMS based Information Systems: Basic Approach – Simple views and High level language (2) Provide simple views (External Schema) and high level language (e.g. SQL) for users to manipulate (handle) data High level language: e.g. SQL (Structured Query Language) <e.g.>: SELECT SNAME FROM S WHERE S#= 'S4'; Description of user's view of data is the "external schema" or "subschema" or "view". High-level languages (Query Language): SQL (1) Data Definition Language: define format (2) Data Manipulation Language: retrieve, insert, delete, update Emphasize: EASE OF USE !! name DBMS based Information Systems: Basic Approach - Storage/Access Method : 1-8 DBMS based Information Systems: Basic Approach - Storage/Access Method (3) Efficient Storage/Access Techniques: implemented once rather than duplicated in all application programs. DBMS based Information Systems: Basic Approach - Transaction Management : 1-9 DBMS based Information Systems: Basic Approach - Transaction Management (4) Provide Transaction Management: Concurrency Control Recovery Security . : Example: A Simple Query Processing : 1-10 Example: A Simple Query Processing Query in SQL： SELECT CUSTOMER. NAME FROM CUSTOMER, INVOICE WHERE REGION = 'N.Y.' AND AMOUNT > 10000 AND CUTOMER.C#=INVOICE.C Operator : SCAN C using region index, create C SCAN I using amount index, create I SORT C?and I?on C# JOIN C?and I?on C# EXTRACT name field Calls to Access Method： OPEN SCAN on C with region index GET next tuple . . . Calls to file system： GET10th to 25th bytes from block #6 of file #5 1.2 An Overview of a Database System : 1-11 1.2 An Overview of a Database System An Example : 1-12 An Example The Wine Cellar Database: Cellar: Retrieval: DML (Data Manipulation Language): SELECT Wine, Bin, Producer FROM Cellar WHERE Ready = 85; Result: An Example (cont.) : 1-13 An Example (cont.) Deletion: DML: DELETE FROM Cellar WHERE Ready < 86; Result: Insertion: DML: INSERT INTO Cellar VALUES (53, 'Pinot Noir', 'Franciscan', 79, 1, 86, 'for Joan'); Result: 43 Cab. Sauvignon Robt. Mondavi 77 12 87 51 Pinot Noir Ch. St. Jean 78 2 86 Bin Wine Producer Year Bottle Ready Comments An Example (cont.) : 1-14 An Example (cont.) Update DML: UPDATE Cellar SET Bottles = 4 WHERE Bin = 51; Result: 43 Cab. Sauvignon Robt. Mondavi 77 12 87 51 Pinot Noir Ch. St. Jean 78 4 86 53 Pinot Noir Franciscan 79 1 86 for Joan Bin Wine Producer Year Bottle Ready Comments What is a Database System? : 1-15 What is a Database System? What is a Database System? (cont.) : 1-16 What is a Database System? (cont.) Major components of a database system: Data: integrated and shared. Hardware: disk, CPU, Main Memory, ... Software: DBMS Users: 1. Application programmers 2. End users 3. Database administrator (DBA) Defining external schema Defining conceptual schema Defining internal schema Liaison with users Defining security and integrity checks Defining backup and recovery procedures Monitoring performance and changing requirements Why Database ? : 1-17 Why Database ? Redundancy can be reduced Inconsistency can be avoided The data can be shared Standards can be enforced Security restrictions can be applied Integrity can be maintained Provision of data independence objective ! Data Independence : 1-18 Data Independence Application Program => Data Structure Immunity of application to change in storage structure and access strategy. Data Dependence vs. Data Independence : 1-19 Data Dependence vs. Data Independence Data Dependent e.g. SELECT CITY FROM S WHERE ITEM = 'X'; Linked list: TOP if item = TOP. item then ......... Tree: . if item < root.data then root := root.left .......... Array: if A[I] = item then ............ Storage structure changed program changed 1.3 An Architecture for aDatabase System : 1-20 1.3 An Architecture for aDatabase System Slide 21: 1-21 An Example of the Three Levels : 1-22 An Example of the Three Levels Internal level : STORED_EMP length = 18 PREFIX TYPE = BYTE(6), OFFSET = 0, INDEX = EMPX EMP# TYPE = BYTE(6), OFFSET=0, DEPT# TYPE = BYTE(4), OFFSET = 12 PAY TYPE = FULLWORD, OFFSET = 16 Conceptual level : EMPLOYEE EMPLOYEE_NUMBER CHARACTER(6) DEPARTMENT_NUMBER CHARACTER(4) SALARY NUMERIC(5) External level : ( PL /I ) DCL 1 EMP 2 EMP# CHAR(6) 2 SAL FIXED BIN(31) (COBOL) 01 EMPC 02 EMPNO PIC X(4) 02 DEPTNO PIC X(4) Functions of the DBMS : 1-23 Functions of the DBMS Data Definition Language (DDL) Data Manipulation Language (DML) Data Security and Integrity (p.267, 508) Data Recovery and Concurrency Data Dictionary Performance Slide 24: 1-24 1.4 Database Technology Trends Distributed Databases : 1-25 Distributed Databases Database Distributed System Distributed database is a database that is not stored in its entirety at a single physical location, but rather is spread across a network of computer. < e.g.> Distributed Databases (cont.) : 1-26 Distributed Databases (cont.) Advantages: efficiency of local processing data sharing Disadvantages: communication overhead implementation difficulties Reference: S. Ceri and G. Pelagatti "Distributed Databases: principles and systems" Multi-Database/Heterogeneous Database : 1-27 Multi-Database/Heterogeneous Database DB + AI : 1-28 DB + AI KBMS : 1-29 KBMS A Combined Model : Logic Programming + Relational DB Three layers : OODB : 1-30 OODB A typical Document : MEMO [Woelk86, SIGMOD] Use of a Database Management System in Design and Application : 1-31 Use of a Database Management System in Design and Application Fuzzy Database : 1-32 Fuzzy Database Fuzzy Query <e.g.> SELECT STUDENT.NAME FROM STUDENT WHERE SEX = M AND HEIGH = TALLER AND WEIGH = SLIMMER STUDENT: <e.g.> SELECT STUDENT.NAME FROM STUDENT WHERE IQ >= 130 More? : 1-33 More? DB AI DB VR ? ? DB ? WWW 1993 1995 1997 DB ? Mobile/video 1999 ? 2002 DB 911/ Anthrax ? 2001 DB DNA/BioInfo. ? 2003 DB ??? 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