DATABASES Pindaro Demertzoglou – Lally School of Management and Technology.

DATABASESPindaro Demertzoglou – Lally School of Management and Technology

Microcomputers and applications

THE OPERATIONAL, TACTICAL, AND STRATEGIC AREAS OF AN ORGANIZATION

Strategic

Tactical

Transactional/Ops


Application Layer

TPS ARCHITECTURE

Data Layer

Sales/Marketing HRFinance/Accounting Operations

Spreadsheet Data

MS Access

AccountsReceivable

AccountsPayable

InvestmentManagement

Oracle Database

QuotationProcessing

OrderProcessing

ClaimsProcessing

Spreadsheet

Oracle Database

Foxpro

RecruitingCareer Planning

CompensationManagement

Excel

Excel

Excel

ProductionPlanning

Product Development

Maintenance Planning

Oracle

Excel

Oracle


OPERATIONS AND ORGANIZATIONAL EFFICIENCY

Management in lean times and cost reduction. Corporate operations and Operating Expenses

in the Income Statement The goal is to reduce inefficiency. We reduce inefficiency by reducing operating

expenses. We reduce operating expenses by creating a

leaner TPS system. A leaner TPS system means reduced cycle

times and reduced cost. As a consequence we have reduced risk from

variations in the market.


TYPES OF DATABASES

According to License Type Commercial (Oracle, Microsoft SQL server, IBM DB2) Open Source (PostgreSQL)

According to Network Architecture Desktop (MS Access) Client-Server (Oracle, IBM DB2, MS SQL)


THE DATABASE MARKET

Let us have a look at the database market.


DATABASE TABLES

Tables (entities) Fields (Attributes) Data types (text, number, Currency, Binary) Records (A group of related fields)

Keys Primary Foreign One-field keys Concatenated keys Natural keys Surrogate keys (Artificial)


RELATIONSHIPS One to one

relationships

One to many relationships

Many to many relationships


ENTITY RELATIONSHIP DIAGRAM


REFERENTIAL INTEGRITY Referential integrity in relational databases means

that relationships among joined tables remain consistent.

That is, if we have a one-to-many relationship between customers and orders: We cannot delete a customer for whom we have orders. We cannot add an order without having a customer. We can have however customers without orders.

Orphaned Records. With referential integrity on, we avoid orphaned records. For example, an order without a customer.

However, we can have customers without orders which is a business fact.


INDEXES

• Indexes improve data retrieval.

• They work great with WHERE and ORDER BY clauses.

• Indexes slow down data inserts and updates since updates and inserts need to be saved at both the table and the index.

• Increase storage requirements.

• Unique indexes can be used as constraints.

• Avoid their usage in small tables with few records. Better used in large tables.

• All primary key fields are automatically indexed when created.

• We can also have multiple-field indexes.


INDEXES


NORMALIZATION

A two-aim process: Redundancy (Elimination of duplicated data) Inconsistent Dependency (Data should be related to

entities ie. Orders must be in a separate table rather than in the customer table)

First Normal Form (Do not use multiple fields in a table to store similar data. Ie. five fields in an inventory table to identify vendors. What happens if we add a new vendor?)

Second Normal Form (Do not store the same data in multiple tables. Ie An address is needed in the customer’s table, shipping, billing etc.) create a separate table for addresses.

Third Normal Form (Exclude from the table fields that do not depend on the key ie For example instead of storing the zip code in the address table that you created above you create a separate table for zip codes.) Not always practical.

Remember: business rules have priority.


CASCADE UPDATES AND DELETES

Cascade deletes allow us to delete an entity record and all associated information to that entity record.

For example, if cascade deletes are on between the tables customers and orders, then when we delete a customer, all related orders will be deleted by the database engine.

Cascade updates let us update all primary keys of an entity and their related foreign keys in all related tables.

For example, if cascade updates are on between the tables customers and orders, then when we update the PK value of a customer, all related foreign keys of that customer in the table orders will be updated by the database engine.


QUERIES SQL statements through which we can select,

delete, insert, and update data. With queries we obtain a subset of attributes, or a

subset of records, or a subset of attributes and records.

They can function as a security mechanism so that end users do not have direct access to tables.

Views can present data from multiple different related tables in a simplified datasheet.

Queries can aggregate data for information generation.

Views do not consume any space, we just store the SQL statement which we can execute at any moment.


SQL Language Data Definition Language Data Manipulation Language

CREATE TABLE Customer1 (

[CustomerID] Counter PRIMARY KEY NOT NULL,

[LastName] text(50) NOT NULL,

[FirstName] text(50),

[Address] text(50));


SQL LANGUAGE (DATA MANIPULATION LANGUAGE)

Select statements Example: Select * from products

Insert statements

Example: Insert into products (productname, unitprice) values ('myproduct', 22)

Update statements

Example: update products set unitprice = unitprice*1.2

Delete statements

Example: Delete from products where productID=70


DATA DICTIONARIES

They are used for development purposes and they consist of a spreadsheet that includes the names of the fields and a description of their purpose in the database.


CLASS EXERCISE

Create a database entity relationship diagram of faculty, courses, and students.

DATABASES Pindaro Demertzoglou – Lally School of Management and Technology.

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