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Summary of the main concepts of DBMS (Part 1) Summary of the main concepts of DBMS (Part 1) Prepared by: Mahmoud Rafeek Alfarra Lecturer in CST- Khan younis Data is a stored representation of meaningful objects and events, as Mahmoud, Ali, Apple, car, Exam, Football Match. Data can be one of two categories Structured: This can be formatted as numbers, text, dates. Unstructured: This can't be formatted as images, video, documents, audio. Information is a processed data to increase knowledge in the person using the data. Database is an organized collection of logically related data. Metadata (data dictionary, system catalog, data about): data that describes the properties and context of user data. Prepared by: Mahmoud Rafeek Alfarra Lecturer in CST- Khan younis March 2011 1 Summary of the main concepts of DBMS (Part 1) 2 Database Management System(DBMS) is a software system that is used to create, maintain, and provide controlled access to user databases DBMS DBMS manages data resources like an operating system manages hardware resources. Components of the database environment: Prepared by: Mahmoud Rafeek Alfarra Lecturer in CST- Khan younis March 2011 Summary of the main concepts of DBMS (Part 1) 3 Data base support Multiple Views of the Data by derived many views (which is a subset of the database but is not explicitly stored). Multiple users can access the database at the same time (which is the concurrency control software: Ensure that several users trying to update the same data do so in a controlled manner) Using transaction which is executing program or process that includes one or more database operations, has two properties: Isolation property: transaction not related to others Atomicity property: Either all the database operations in a transaction are executed or none are. Three-Schema Architecture: Internal level : Describes physical storage structure of the database Conceptual level: Describes structure of the whole database for a community of users External or view level: Describes part of the database that a particular user group is interested in. Prepared by: Mahmoud Rafeek Alfarra Lecturer in CST- Khan younis March 2011 Summary of the main concepts of DBMS (Part 1) Phases of designing a database: designing data base means how the data base will be built in the different steps which are (External, internal). 1. External schema contains two steps which are (Requirements specification and analysis) and (Conceptual design) which includes identification of important entity and relationship that is what is the data to be represented. 2. Internal Schema contains two designing steps which are (Logical design) and (Physical design). Logical design: To translate the conceptual representation to the logical structure of the database, this includes the designing of relations. Physical design: To allow the designer to decide how the logical structure is to be physically implemented on the target DBMS (How is the data stored in memory?). The conceptual representation of data does not include details of how data is stored or how operations are implemented. Data model: An integrated collection of concepts for describing data, relationships between data, and constrains on the data in an organization. (Representation of the data base steps ) Categories of Data Models: Relational data model Object data model Physical data models Database schema: the overall description of the database. (According to 3-arch.) External schema: multiple conceptual schema: one (data items & relation) internal schema: one (contains the stored procedure and method) Prepared by: Mahmoud Rafeek Alfarra Lecturer in CST- Khan younis March 2011 4 Summary of the main concepts of DBMS (Part 1) DBMS is responsible for mapping between these three types of schema. DBMS Languages Data definition language (DDL): Defines both schemas Storage definition language (SDL): Specifies the internal schema View definition language (VDL): Specifies user views/mappings to conceptual schema Data manipulation language (DML): Allows retrieval, insertion, deletion, modification. Prepared by: Mahmoud Rafeek Alfarra Lecturer in CST- Khan younis March 2011 5