Introduction to Database Technology Elmasri/Navathe ch 1-2 Padron-McCarthy/Risch ch 1 Sobhan Badiozamany Silvia Stefanova Department of Information Te

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35 DATABASE DESIGN I - 1DL300 Spring 2013 An Introductory Course on Database Systems Uppsala Database Laboratory Department of Information Technology, Uppsala University, Uppsala, Sweden Silvia Stefanova, UDBL - IT - UU

36 Introduction to Database Technology Elmasri/Navathe ch 1-2 Padron-McCarthy/Risch ch 1 Sobhan Badiozamany Silvia Stefanova Department of Information Technology Uppsala University, Uppsala, Sweden Silvia Stefanova, UDBL - IT - UU

37 Outline 1. Data Model, Database Schema Categories of data models Database schemas and instances 2. Data Independence Three-schema architecture Logical independence Physical independence 3. Database Languages 4. Classification of DBMS 5. To Summarize Silvia Stefanova, UDBL - IT - UU

38 Outline 1. Data Model, Database Schema Data models, categories of data models Database schemas and instances 2. Data Independence Three-schema architecture Logical independence Physical independence 3. Database Languages 4. Classification of DBMS 5. To Summarize Silvia Stefanova, UDBL - IT - UU

39 Data Model??? Silvia Stefanova, UDBL - IT - UU

40 Data Model Data Model: A collection of concepts that can be used to describe the structure of database Data Model consists of o Set of concepts: data types, relationships, constraints o Set of basic operations for specifying retrievals and updates on the database Every database has a data model which makes it possible to hide the physical representation of data Silvia Stefanova, UDBL - IT - UU

41 Categories of data models High-level (conceptual) : close to how users perceive data o ER (Entity-Relationship) model Low-level (physical): details of how data is stored on computers Representational (implementation): in between conceptual and physical o Relational (ORACLE, DB2, SQL Server, MySQL, Mimer) o Object-oriented (ObjectStore, Objectivity, Versant, Poet) o Object-relational (Informix, Odapter, DB2) o Hierarchical (IMS) o Network (IDMS) Silvia Stefanova, UDBL - IT - UU

42 What is the difference between database and database description? Silvia Stefanova, UDBL - IT - UU

43 Database Schema and Instances Database schema: the database description specified during the database design and not expected to change The actual data in the database may change frequently Database instance (state): the data in the database at a particular moment. Every change of data creates a new instance of the database. o Valid state: satisfies the structure and constraints in the database schema o Meta-data: description of the schema (data about data) Silvia Stefanova, UDBL - IT - UU

44 Outline 1. Data Model, Database Schema Categories of data models Database schemas and instances 2. Data Independence Three-schema architecture Logical independence Physical independence 3. Database Languages 4. Classification of DBMS 5. To Summarize Silvia Stefanova, UDBL - IT - UU

45 Three-schema Architecture End users External level view 1 view 2 view n Conceptual level Conceptual schema Internal level Internal schema Database instance Silvia Stefanova, UDBL - IT - UU

46 Internal level Three-schema Architecture o Described the physical storage structure of the database o Uses a physical data model (internal schema) Conceptual level o Describes the structure of the whole database for community of users; describes entities, data types, relationships, user operations o Uses a representation data model External (view) level o Describes the part of the database that a particular user group is interested in; hides the rest from that group o Has a number of external schemas Silvia Stefanova, UDBL - IT - UU

47 What is the goal with the three-schema architecture? Silvia Stefanova, UDBL - IT - UU

48 Data Independence Data Independence: The capacity to change the schema at one level of a database system without having to change at the next higher level Silvia Stefanova, UDBL - IT - UU

49 Data Independence Logical Independence: The capacity to change the conceptual schema without having to change the external schema o Example: Add another field to a conceptual schema Physical Independence: The capacity to change the internal schema without having to change the conceptual schema o Example: Put an access path(index) to reorganize the files Silvia Stefanova, UDBL - IT - UU

50 Outline 1. Data Model, Database Schema Categories of data models Database schemas and instances 2. Data Independence Three-schema architecture Logical independence Physical independence 3. Database Languages 4. Classification of DBMS 5. To Summarize Silvia Stefanova, UDBL - IT - UU

51 Database Languages Database Language: Generic term for a class of languages used for defining, communicating with or manipulating a database. Storage Definition Language (SDL) to specify internal schema Data Definition Language (DDL) to specify conceptual schema View Definition Language (VDL) to specify user views Data Manipulation Language (DML) to manipulate the data: insert, delete, update) Silvia Stefanova, UDBL - IT - UU

52 Database Languages In the DDL the database administrator define the internal and conceptual schema and in this manner the database is designed. Subsequent modifications in the schema design is also made in DDL. The DML used by DB users and application programs retrieve, add, remove, or alter the information in the database. SQL represents a combination of DDL, VDL and DML Silvia Stefanova, UDBL - IT - UU

53 Outline 1. Data Model, Database Schema Categories of data models Database schemas and instances 2. Data Independence Three-schema architecture Logical independence Physical independence 3. Database Languages 4. Classification of DBMS 5. To Summarize Silvia Stefanova, UDBL - IT - UU

54 Classification of DBMS Criteria data model: o Relational DBMS o Object-oriented DBMS o Object-relational DBMS o Graph DBMS Criteria number of sites on which database is distributed o Centralized DBMS o Distributed DBMS Silvia Stefanova, UDBL - IT - UU

55 Classification of DBMS Criteria number of users: o Single-user DBMS o Multi-user DBMS Criteria purpose o General purpose DBMS o Special-purpose DBMS Silvia Stefanova, UDBL - IT - UU

56 Outline 1. Data Model, Database Schema Categories of data models Database schemas and instances 2. Data Independence Three-schema architecture Logical independence Physical independence 3. Database Languages 4. Classification of DBMS 5. To Summarize Silvia Stefanova, UDBL - IT - UU

57 Summary Data model Database schema, database instance Data independence Silvia Stefanova, UDBL - IT - UU

58 Components of a DBMS (Figure 2.3 Elmasri/Navathe) Silvia Stefanova, UDBL - IT - UU