ReLaTiOnAL DaTaBaSe FuNdAmEnTaLs:-
vInformation is everywhere in an organization.
vInformation is stored in databases.
§Database – maintains information about various types of objects (inventory), events (transactions), people (employees), and places (warehouses).
vDatabase models include:
§Hierarchical database model – information is organized into a tree-like structure (using parent/child relationships) in such a way that it cannot have too many relationships.
§Network database model – a flexible way of representing objects and their relationships.
§Relational database model – stores information in the form of logically related two-dimensional tables.
EnTiTiEs aNd AttRiBuTeS:-
vEntity – a person, place, thing, transaction, or event about which information is stored.
§The rows in each table contain the entities.
§In Figure 7.1 CUSTOMER includes Dave’s Sub Shop and Pizza Palace entities.
vAttributes (fields, columns) – characteristics or properties of an entity class.
§The columns in each table contain the attributes.
§In Figure 7.1 attributes for CUSTOMER include Customer ID, Customer Name, Contact Name.
KeYs aNd ReLaTiOnShiPs:-
vPrimary keys and foreign keys identify the various entity classes (tables) in the database.
§Primary key – a field (or group of fields) that uniquely identifies a given entity in a table.
§Foreign key – a primary key of one table that appears an attribute in another table and acts to provide a logical relationship among the two tables.
vPotential relational database for Coca-Cola:
Walk your students through the relational database model in Figure 7.1
To ensure your students are grasping the concepts, ask them to answer the following:
How many orders have been placed for T’s Fun Zone?
Answer: 1 Order IT 34563.
How many orders have been placed for Pizza Palace?
How many items are included in Dave’s Sub Shop’s two orders?
Answer: Order 34561 has 3 items and order 34562 has one item for a total of 4 items in both orders.
Who is responsible for distributing Dave’s Sub Shop’s orders?
Answer: Hawkins Shipping.
Which products are included in Order 34562?
Answer: 300 Vanilla Coke.
ReLaTiOnAL DaTaBaSe AdVaNtaGeS:-
vDatabase advantages from a business perspective include:
§Increased scalability and performance.
§Reduced information redundancy.
§Increased information integrity (quality).
§Increased information security.
vA well-designed database should:
§Handle changes quickly and easily.
§Provide users with different views.
§Have only one physical view.
•Physical view – deals with the physical storage of information on a storage device.
§Have multiple logical views.
•Logical view – focuses on how users logically access information.
InCreAsEd ScALaBiLiTy aNd PeRfOrMaNcE:-
vA database must scale to meet increased demand, while maintaining acceptable performance levels.
§Scalability – refers to how well a system can adapt to increased demands.
§Performance – measures how quickly a system performs a certain process or transaction.
ReDuCed InFoRmAtiOn ReDuNdAnCy:-
vDatabases reduce information redundancy.
§Redundancy – the duplication of information or storing the same information in multiple places.
vInconsistency is one of the primary problems with redundant information.
InCrEaSe InFoRmAtiOn InTeGriTy (QuAliTy):-
vInformation integrity – measures the quality of information.
vIntegrity constraint – rules that help ensure the quality of information.
§Relational integrity constraint - rule that enforces basic and fundamental information-based constraints.
§Business-critical integrity constraint - rule that enforce business rules vital to an organization’s success and often require more insight and knowledge than relational integrity constraints.
InCreAsEd InFoRmAtiOn SeCuRiTy:-
vInformation is an organizational asset and must be protected.
vDatabases offer several security features including:
§Password – provides authentication of the user.
§Access level – determines who has access to the different types of information.
§Access control – determines types of user access, such as read-only access.
Database Management Systems:-
vDatabase management systems (DBMS) – software through which users and application programs interact with a database.
Direct interaction :
>The user interacts directly with the DBMS.
>The DBMS obtains the information from the database.
>User interacts with an application (i.e., payroll application, manufacturing application, sales application).
>The application interacts with the DBMS.
>The DBMS obtains the information from the database.
DaTa-DrIvEn WeB SiTeS:-
>A data-driven Web site is an interactive Web Site kept constantly updated and relevant to the needs of its customers through the use of a database. Data-driven Web sites are especially useful when the site offers a great deal of information, products, or services. Web site visitors are frequently angered if they are buried under an avalanche of information when searching a Web site. A data-driven Web site invites visitors to select and view what they are interested in by inserting a query, which the Web site then analyzes and custom builds a Web page in real-time that satisfies the query. The figure displays a Wikipedia user querying business intelligence and the database sending back the appropriate Web page that satisfies the user’s request.
>What would happen to a Web site that is not data-driven?
Answer:The users would need to continually update the Web site data manually as the business data is updated. This would be a redundant effort and most likely result in errors and the Web site could quickly become out of sync with the business data.
DaTa DriVeN WeB SiTe AdVaNtaGeS:-
1. Development: Allows the Web site owner to make changes any time—all without having to rely on a developer or knowing HTML programming. A well-structured, data-driven Web site enables updating with little or no training.
2. Content management: A static Web site requires a programmer to make updates. This adds an unnecessary layer between the business and its Web content, which can lead to misunderstandings and slow turnarounds for desired changes.
3. Future expandability: Having a data-driven Web site enables the site to grow faster than would be possible with a static site. Changing the layout, displays, and functionality of the site (adding more features and sections) is easier with a data-driven solution.
4. Minimizing human error: Even the most competent programmer charged with the task of maintaining many pages will overlook things and make mistakes. This will lead to bugs and inconsistencies that can be time consuming and expensive to track down and fix. Unfortunately, users who come across these bugs will likely become irritated and may leave the site. A well-designed, data-driven Web site will have ”error trapping” mechanisms to ensure that required information is filled out correctly and that content is entered and displayed in its correct format.
5.Cutting production and update costs: A data-driven Web site can be updated and ”published” by any competent data entry or administrative person. In addition to being convenient and more affordable, changes and updates will take a fraction of the time that they would with a static site. While training a competent programmer can take months or even years, training a data entry person can be done in 30 to 60 minutes.
6.More efficient: By their very nature, computers are excellent at keeping volumes of information intact. With a data-driven solution, the system keeps track of the templates, so users do not have to. Global changes to layout, navigation, or site structure would need to be programmed only once, in one place, and the site itself will take care of propagating those changes to the appropriate pages and areas. A data-driven infrastructure will improve the reliability and stability of a Web site, while greatly reducing the chance of ”breaking” some part of the site when adding new areas.
7. Improved Stability: Any programmer who has to update a Web site from ”static” templates must be very organized to keep track of all the source files. If a programmer leaves unexpectedly, it could involve re-creating existing work if those source files cannot be found. Plus, if there were any changes to the templates, the new programmer must be careful to use only the latest version. With a data-driven Web site, there is peace of mind, knowing the content is never lost—even if your programmer is.
DaTa-DriVeN BuSinEsS InTelliGeNcE:-
vBusiness Intelligence in a data-driven Web site:
>Companies can gain business intelligence by viewing the data accessed and analyzed from their Web site. The figure displays how running queries or using analytical tools, such as a Pivot Table, on the database that is attached to the Web site can offer insight into the business, such as items browsed, frequent requests, items bought together, etc.
AmOnG MuLtiPlE DaTabAsEs:-
vIntegration – allows separate systems to communicate directly with each other.
§Forward integration – takes information entered into a given system and sends it automatically to all downstream systems and processes.
§Backward integration – takes information entered into a given system and sends it automatically to all upstream systems and processes.
>Basically, all information flows forward along the business process. Sales enters the information when it is negotiating the sale (looking for opportunities). The information is then passed to the order entry system when the order is actually placed. The order fulfillment system picks the products from the warehouse, packs the products, labels boxes, etc. Once the order is filled and shipped, the customer is billed.
What would happen if users could enter order information directly into the billing system?
The systems would quickly become out-of-sync. There might be bills for nonexistent orders, or orders that do not have any bills (if someone deleted a bill). For this reason organizations typically place a business-critical integrity constraint on integrated systems: With a forward integration the information must be entered in the sales system, you could not enter information directly into the billing system.
>Integrations are expensive to build and maintain and difficult to implement. For these reasons many organizations only build forward integrations and use business-critical integrity constraints to ensure all information is always entered only at the start of the integration (one source of record).
>Basically, all information flows backward along the business process. Billing enters information and this information is passed back to the order system. The order fulfillment system passes the information back to the order entry system. The order entry system passes the information back to the sales system.
Why would an organization want to build both forward and backward integrations?
This allows users to enter information at any point in the business process and the information is automatically sent upstream and downstream to all other systems. For example, if order fulfillment determined that they could not fulfill an order (the product had been discontinued), they could simply enter this information into the database and it would be sent automatically upstream to the sales representative who could contact the customer and downstream to billing to remove the item from the bill.
Building a central repository specifically for integrated information:-
The above figure displays an example of customer information integrated using this method. Users can create, read, update, and delete in the main customer repository, and it is automatically sent to all of the other databases. This method does not follow the business process when building the integrations. Business-critical integrity constraints still need to be built to ensure information is only ever entered into the customer repository, otherwise the information will become out-of-sync.