Based on G. Post, Database Management Systems University of Manitoba Asper School of Business 3500 DBMS Bob Travica Updated 2015 Chapter 1 Introduction

DBSYSTEMS 2 of 15 Basic Concepts of Database Systems  Database is  A collection of data organized in some way grouped on what they refer to, or on technical types relationships between pieces of data determined  Data = symbols for recording and communication (e.g., customer ID and name)  Example: Think of records (paper, electronic) describing employees.  The organization of data can be explained by metadata.  Metadata define how data are organized (e.g., Employee is a class of data, which has x number of attributes, and each attribute belongs to a data type). More  EmployeeIDNumber LastNameText FirstNameText PhoneNumber

DBSYSTEMS 3 of 15 Basic Concepts  Database Management System (DBMS)  Software for creating databases, storing & retrieving data, creating user interface (forms), creating reports, and administering a DB system (security, access, etc.).  DBMS Product (a specific DBMS software; same as “DBMS Brand”).  Database System (DBMS Application, Application)*:  An implementation of a DBMS product including one or more databases, logic (business rules), some code, and user interface. Supporting various information needs.  An information system that results from “applying” a DBMS or a database. Supporting specific information needs.

DBSYSTEMS 4 of 15 File (Processing) Systems vs. DB systems (DBS)  History but also a frequent shortcut today (e.g., Excel as surrogate of DBS)  File Processing Systems:  Data files and program files (code) that work on data files, or  Data and code in the same file  Separate code (functionality) for data input, modification, retrieval, & deletion.  Data files are closely coupled with programs that define metadata - tight coupling reducing design flexibility (changes). More 

DBSYSTEMS 5 of 15 DBS are:  Higher on retrieval capabilities  Lower redundancy, higher data integrity  Data independent from programs (code); looser coupling – changes in data and code less restricted  Better security and management of concurrent access to database  Significantly lower development and maintenance cost  But keep in mind: Excel’s enduring popularity in companies. File (Processing) Systems vs. DB systems

DBSYSTEMS 6 of 15 Modifying Data in DBS -- Data-Program independence  Add cell tel. number to employee table  Open table template  Add data element  Existing reports, queries, code will not crash although need to be modified to output new data – looser coupling Field NameData TypeDescription EmployeeIDNumberAutonumber.. TaxpayerIDTextFederal ID LastNameText FirstNameText... PhoneTextPhone Number... CellPhoneTextCell Phone No.

DBSYSTEMS 7 of 15 DB System Components Database Engine: CRUD* operations & Data Dictionary Concurrency & Lock Manager Recovery Manager Disk Space Manager Query Processor Form Builder Report Writer Application Generator Data & Metadata Management Security Management D B M S Database Retrieval Input/Output; User Interface System development tools *CRUD= Create, Read, Update, Delete Note: The Post book mixes “database” With “data” and “application”.

DBSYSTEMS 8 of 15 Creating Outputs via Report Writer Output: Report Database Database Engine Report Writer 1 Query Processor

DBSYSTEMS 9 of 15 Relational Database Standard  “Relation” = table, a logical view of the data structure for storing data. An example of Table (Sale) created in Oracle.

DBSYSTEMS 10 of 15 Examples of Relational DBMS Products  Oracle  Sybase  Informix (Unix)  DB2, SQL/DS (IBM)  Access, SQL Server (Microsoft)  Many limited to PC (MS Access, dBASE, Paradox, …)  Open source: MySQL (more)more

DBSYSTEMS 11 of 15 Hierarchical Database Item#ItemNameQuantity 998Dog Food12 764Cat Food11 Items Order files Customers files To retrieve how many of item A are sold, start at the top from Customer. Then all nested data are retrieved top-down and left-right. Different data models needed for different retrieval tasks (e.g., Order at the root) => high data redundancy in DBS! Customer XYZ Order 1 Item A Order 2 Item B Item A Item C Entry point pointers First commercial standard (IBM’s IMS) Still used in legacy systems

DBSYSTEMS 12 of 15 Network Database Customer XYZ Order 1Order 2 Entry point Entry points Item A Item B Item C One data model supports different retrieval paths (by customer, order, item). Relationships between records also supported by pointers; complex programming.

DBSYSTEMS 13 of 15 Relational Database Customer(CustomerID, Name, …) Order(OrderID, CustomerID, OrderDate, …) ItemOrdered(OrderID, ItemID, Quantity, …) Item(ItemID, Description, Price, …) Data organized as logical tables, consisted of rows (records) and columns (attributes), and connected via key attributes. Possible to retrieve almost any combination of rows and columns, and a specific piece of data (field) within a row. Pointers transparent to developers, just need to specify Primary Key (PK)—Foreign Key (FK) relationships. Primary Key (PK, Key) Foreign Key (FK)

DBSYSTEMS 14 of 15 Object-Oriented Databases Inheritance in Generalization/Speci- alization relationship Customer CustomerID Name … Add Customer Drop Customer Change Address… Government Customer ContactName ContactPhone Discount, … NewContact Corporate ContactName ContactPhone … AddNewContact Order OrderID CustomerID … NewOrder DeleteOrder … Procedures (behavior, methods) for processing data. Data Pure OODB: a storage of objects with various retrieval techniques depending on objects’ APIs. Rare in business. Extends data types and methods over relational DB. Takes advantages of OO capabilities (e.g., inheritance).

DBSYSTEMS 15 of 15 Object-Relational DB Systems  More frequent than pure object-oriented systems  Architecture:  Database is relational  Objects are created in main memory according to class diagram and business rules, and populated by data from the relational databases (data access layer in system sequence diagrams). Extended data and method capabilities in objects.  System operations are performed by objects