Chapter 5 Notes

Most widely used structure data elements are stored in

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Unformatted text preview: nts are stored in tables Row represents a record; column is a field Can relate data in one file with data in another, if both files share a common data element For example… Object­oriented Structure An object database (also object-oriented database management system) is a database management system in which information is represented in the form of objects as used in objectoriented programming. Object databases are different from relational databases which are tableoriented. Object-relational databases are a hybrid of both approaches. For example… Principles of Information Systems, Fifth Edition Multidimensional Structure A multidimensional database is a form of database that is structured to optimize online analytical processing (OLAP) and data warehouse applications. It can receive data from a variety of relational databases and structure the information into categories and sections that can be accessed in a number of different ways. For example… Evaluation of Database Structures • Hierarchical – – • Network – – • Works for structured, routine transactions Can’t handle many-to-many relationships More flexible than hierarchical Unable to handle ad hoc requests Relational – – – Easily responds to ad hoc requests Easier to work with and maintain Not as efficient/quick as hierarchical or network Relational Operations Select rows Project columns using a particular criteria to eliminate rows involves eliminating columns in a table Join tables combine or link two or more tables using common data attributes Database Basics Good database design will get you through poor programming better than good programming will get you through poor database design…. Relational Database Definition: Data stored in tables that are associated by shared attributes (keys). Any data element (or entity) can be found in the database through the name of the table, the attribute name, and the value of the primary key. Relational Database Definitions Entity: Object, Concept or event (subject) Attribute: a Characteristic of an entity Row or Record: the specific characteristics of one entity Table: a collection of records Database: a collection of tables The Relational Database model Developed by E.F. Codd, C.J. Date (70s) Table = Entity = Relation Table row = tuple = instance Table column = attribute Table linkage by values Entity-Relationship Model The Relational Model Each attribute has a unique name within an entity All entries in the column are examples of it Each row is unique Ordering of rows and columns is unimportant Each position (tuple) is limited to a single entry. Data Model: What’s a model? A data model is a representation of reality It’s used to define the storage and manipulation of a data base. Data Models have two components: Structure: the structure of the data stored within Operations: Facilities for manipulation of the data. Relational Database Systems Most popular DBMS model for GIS Flexible approach to linkages between records comes the closest to modeling the complexity of spatial relationships between objects. CRUD ! Refers to the most...
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