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 HierarchicalNetworkRelational ConceptualizationModerately Easy DifficultEasy Ease of DesignVery Difficult Moderately Difficult Difficult Ease of MaintenanceDifficultVery DifficultEasy Data RedundancyHighLow Ease of UseModerateLowHigh

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. 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? db Distributed db

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

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

20. 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?

21. Discussion questions  Discussion questions, pg 446-47: 17, 22, 25, and 32