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Announcements

Announcements. Data Management. Chapter 12. Traditional File Approach. Structure Field  Record  File Fixed All records have common fields, and a field is the same size across all records Variable Variable number of fields within a record Variable size for a field across records.

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Announcements

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  1. Announcements

  2. Data Management Chapter 12

  3. Traditional File Approach • Structure • Field  Record  File • Fixed • All records have common fields, and a field is the same size across all records • Variable • Variable number of fields within a record • Variable size for a field across records

  4. Traditional File Structures • Sequential Access • Batch Process • Master File Updates • Indexed Files • Use an index to locate a specific record • Indexed-Sequential • Way to store data sequentially and use indices to access

  5. Traditional File Approach – cont’d • Advantages • Simplicity • Efficiency • Customization • Disadvantages • Program/Data Dependency • Data Redundancy • Data Integrity

  6. Moving to Database Management System (DBMS) • Advantages • Reduced data redundancy • Application/data independence • Better control • Security: Giving users different views addresses security issue • Flexibility • Queries: Request data from specified fields

  7. Database Models • The Hierarchical Model • Records are related hierarchically -- each category is a subcategory of the next level up • Disadvantages of hierarchical databases • To retrieve a record, a user must start at the root and navigate the hierarchy. • If a link is broken, the entire branch is lost. • Requires considerable data redundancy

  8. Database Models • The Network Model • Allows a record to be linked to more than one parent • Supports many-to-many (N:M) relationships • Advantage of the network model • Reduced data redundancy • Disadvantages of the network model • Complicated to build and difficult to maintain • Difficult to navigate

  9. Database Models • The Relational Model • Consists of tables; links among entities are maintained with foreign keys • Advantages of relational databases • Same advantages of a network database without the complications • Easier to conceptualize and maintain • Virtually all DBMSs offered for microcomputers accommodate the relational model

  10. Comparison of Data Models

  11. Major Database Products • Hierarchical • Focus, IMS, Btrieve • Network • Adabas, Image • Relational • Access, DB2, dBase V, FoxPro, Paradox • Oracle, Sybase, Rbase, Sql Server

  12. Components of Database Management Systems • The Schema • Describes the structure of the database • The Data Dictionary (Metadata) • Maintains all information supplied by the developer when constructing the schema • Data Definition Language (DDL) • Used to construct the schema • Data Manipulation Language (DML) • Used to query the database

  13. Advantages of using SQL • Structured Query Language (SQL) • International standard DDL and DML for relational DBMS • Users do not need to learn different DDLs and DMLs. • SQL can be embedded in widely used 3rd generation languages, increasing efficiency and effectiveness. • Programmer not forced to rewrite statements since SQL statements are portable.

  14. Database Architecture • Distributed Databases • Replication • Full copy of the entire database is stored at all sites • Fragmentation (distributed) • Parts of database are stored where they are most often accessed

  15. Distributed db db db db db How to best support organizational needs with a DBMS? • Single, large, centralized repository • Promotes maintenance and security • As size of database grew, performance suffered • Broadband still emerging, very expensive • Multiple smaller distributed databases • Some combination • Does everyone need access to real-time data?

  16. Data Warehousing • Data warehouse • Collection of data that supports management decision making • Phases in Building a Data Warehouse • Extraction Phase • Cleansing Phase • Loading Phase

  17. Data Mining • Selecting, exploring, and modeling data to discover unknown relationships • Use data modeling and “AI” techniques

  18. Discussion Questions • Distinguish the traditional file approach from the database approach.  What are the primary differences in terms of how they store data? • What are the advantages and disadvantages of the following types of database models: hierarchical, network,  relational, and Object Oriented? • What alternative file-access methods are available to implement a database at the physical level? What factors should you consider when choosing among these alternative methods? • What is a DBMS and what are some of the key components of a DBMS?

  19. Discussion questions • Discussion questions, pg 446-47: 17, 22, 25, and 32

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