1. Database Fundamentals
ITE 370
11/19/2018

2. Databases
A database is a collection of related data which is organized to meet user needs
We assume a relational database model
Relational database design objectives:
Eliminate redundant data
Be able to locate individual records quickly
Make enhancements to the database easy to implement
Keep the database easy to maintain
Theme for this class – Database Programming
VISUAL
EVENT-DRIVEN
OBJECT-ORIENTED
CONNECT TO DATABASE
We will learn techniques to connect through a visual, OO, event-driven program
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3. Entities
An entity is a class of objects, such as people, products, or services, about which we collect data. For example,
Students at the university.
Employees at a business.
Sales transactions in a retail business.
Inventory of parts in a warehouse.
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4. Relations and Tables
A relation is a set of columns and rows collected in a table-like structure that represents a single entity made up of related data
A table is a physical implementation of a relation in a DBMS
A relation does not have to be a physical entity –
It can be the results from a query.
Relations can be NON-normalized
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5. Attributes and Columns
An attribute is a characteristic of an entity
Examples of attributes
Names, addresses, phone numbers of people.
Titles, salaries, job descriptions of employees.
Time, date, customer id, sales person id in a sales transaction.
Part number, Cost, In-stock-quantity of inventory of parts.
A column, or field, is a physical implementation of an attribute
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6. Tuples and Rows
A tuple is set of data whose values make up an instance of each attribute defined for that relation
A tuple is implemented physically as a row in a table, or a record
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7. Summary of basic terms In relational model, or the logical model
Relations consist of a set of tuples that define a set of specific attributes for one instance of the entity
In the physical implementation of a database
Relations are implemented as tables
Attributes are columns or fields
Tuples are rows or records
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8. Keys
Keys are the attributes that are used to uniquely identify each instance of an entity, i.e. each row in a table
The uniqueness can naturally occur like Social Security numbers or can be created by the database management system.
Student Id
Employee number
Part number
Social Security Number
The trend is towards making primary keys unique for the entire database, not just within a specific table
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9. Relationships
Relationships are established between entities. They provide the link between tables. These relationships are usually connected by keys (sometimes called secondary keys). In both entities, the keys contain the unique data that relates the two tables together. Usually, the (primary) key field in one table is linked to a foreign key in another table.
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10. Relationships Relationships may be one-to-one one-to-many
many-to-many (requires intersection table in physical implementation)
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11. Database Review Question
Athletes at the Olympics play for themselves, but they also compete for their country. An athlete belongs to a country – this is their nationality. A country can have more than one athlete representing it, of course, but an athlete can only compete for one country at the Olympics. If the athlete entity is implemented as a database table, and the country entity is implemented as another, then which table(s) contain(s) the foreign key to represent the relationship between the athletes and countries?
Athlete - Both Athlete and Country
Country - Either Athlete or Country
Cardinality defines the numeric relationships between occurrences of the entities on either end of the relationship line.
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12. Bus Schedule Database from an ITE Project Course
Stop – Physical Location of where the bus stops (stops can be on multiple routes or even multiple times on the same route)
StopOnRoute – Bridge Entity between Stop and Route due to M:N relationship
Route – Sequence of Stops to Pick Up and Drop Off Passengers for a single Bus and Driver
(Foreign Keys are in the Main Table)
RouteStart – Allows routes to run multiple times during the day (created through normalization to avoid redundant data in Route table)
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13. Normalization
Rules of normalization are established to organize a relational database so that
Data integrity is preserved
Data redundancy is minimized
Practical limitations sometimes require that data in a database be non-normalized
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14. Relation (not a physical table) result from a Query
Non-normalized
Redundant Data
Can lose data integrity
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15. Brief Introduction to SQL
SQL stands for Structured Query Language, a widely-supported database language that has established standards
SQL is a 4GL? Specifies the “what” rather than the “how”
In SQL, we will write queries. A query is a formalized instruction to a database to either return a set of records or perform a specific action on a set of records as specified in the query
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16. Types of SQL statements
There are 3 types of SQL statements
Data Definition Language (DDL)
Data Control Language (DCL)
Data Manipulation Language (DML)
We will almost exclusively focus on the DML—statements used to view, add, modify, or delete data stored in a relational database
We will deal with DML – Data Manipulation Language – Add, Update, Delete (Manipulate)
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17. How are SQL statements executed?
Four ways. We will focus on two:
Direct invocation
From SQL-Server Query Analyzer
From MS-Access in Query Design
Call Level Interface (CLI)
Applications invoke SQL statements at run-time
SQL statements not precompiled
Executed directly by RDMBS
Where do we put the SQL Statements?
In Database
In Other Application
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18. Direct Invocation via SQL-Server Query Analyzer
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19. A CLI-style call in Visual Basic
In VB:
strSQL = “Select LName, FName From Emp Where Title = ‘Clerk’;”
adoEmp.RecordSource = strSQL
adoEmp.CommandType = adCmdText
adoEmp.Refresh
Or, another example
adoEmp.Open “SELECT * From Emp “ _
& “Where Title = ‘” & cboTitle.Text & “’”
SQL can be assigned as a property of an object
Embedded SQL in Visual Basic (or other languages)
We do not want users to work directly with the database
We need Security
We Need “EASY” for User (GUI)
Some queries we will write in code, in other cases we will write them in stored procedures that we can call from our application
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