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Database, SQL, & ADO.Net

Chapter 19

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Quote for TodayGet your facts first, and then you can

distort them as much as you please.

Mark TwainIt is a capital mistake to theorize

before one has data.Arthur Conan Doyle

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Database SystemsAn integrated collection of related dataProvide file-processing capabilitiesOrganize data to enhance retrieval of data in meaningful ways

Query a question a request for information based on specific criteria

SQL - Structured Query Language (pronounced sequel)

used universally to query databases

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Hierarchy of a DBMSDBMS (DataBase Management System)

      made up of one or more databases

Databases

Tables/Queries/Forms/Reports (also known as files in other databases)

Records

Fields

Characters

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Relational Database Systems

Microsoft SQL ServerOracle ™Sybase ™DB2 ™Informix ™MySQL™Microsoft Access

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Database System Advantages

Redundancy can be reducedInconsistencies can be avoidedData can be sharedStandards can be enforcedSecurity restrictions can be appliedIntegrity can be maintainedConflicting requirements can be balanced

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Database Management System

(DBMS) - where the actual manipulation of the database occurs.

This separation from the user interface simplifies the design process.

EndUser

ApplicationSoftware

Databasemanagement

system

Actualdatabase

Data seen interms of the application

Data seen interms of a database model

Data seen in itsactual organization

Conceptual layers of a database

“UserInterface”

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Data Independence

Applications are separate from how the data is physically stored or accessed.Makes it easy to have different views of the same data by different applications.Data Dependence is an application where the storage

structure and accessing strategy cannot be changed without affecting the application significantly.

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Database Languages

Users interact with data in databases through the use of database languages.Applications can use higher-level languages to interface with databases. VB, C, C++, Java, COBOL, PL/I or Pascal Queries of the database are made

through the use of a query language Structured Query Language (SQL)

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Host Languages

Query languages that make it easy to express requests in the context of a particular application.Each host language ordinarily includes a Database Sublanguage (DSL)

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Database Sublanguage (DSL)

Concerned with the specifics of database objects and operations combination of 2 languages

Data Definition Language (DDL) - facilities for defining database objects

Data Manipulation Language (DML) - provides features for specifying the processing to be performed on database objects.

SQL includes both DDL and DML

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Distributed Database

A database that is spread throughout the computer systems of a network. Provides the control and economics of

local processing with the advantages of information accessibility over a geographically dispersed organization. Each data item is stored at the location in

which it is most frequently used The item remains accessible to other

network users.

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DD - Disadvantages

Costly to ImplementCostly to OperateVulnerable to security violations

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Distributed Databases - Advantage 1

Without a DBMS, the application software would have to know where all of the pieces of the database were stored.

With a DBMS, the application software can be written as if the database were all on one machine.

Pensacola

database

Machine 1

Conceptof one

database Ft. Walton

database

Machine 2

Milton

database

Machine 3

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DD - Advantage 2 Separating the application software from the

DBMS helps control access to the database. By providing different interfaces for different

users, access is controlled.

PayrollUser

ApplicationSoftware

InventoryUser

User Interfaces

Ex. Payroll and Inventory personnel require different parts of the database. By providing each group a different user interface, access is restricted to other areas of the database.

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Old vs. New

CustomerRecords

PayrollRecords

EmployeeRecords

InventoryRecords

CustomerServiceDept.

PayrollDept.

PersonnelDept.

PurchasingDept.

Database-oriented Information System

ConsolidatedDatabase

CustomerServiceDept.

Payroll Dept. Personnel Dept.

PurchasingDept.

File-oriented Information SystemOld

NEW

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DD - Advantage 3The organization of the database can be changed without changing the application software.Supports the concept of data independence.Only the schema used by the central system and the subschemas to those users involved in the change are impacted.

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DD - Advantage 4Software at the application level is written from a simplified, conceptual view of the database rather than the actual, complex, detailed view of the database.VB frequently provides the user interfaces to the database. The database can be written in several different database languages.

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Relational Database ModelLogical representation of data that allows relationships among data to be considered without concern for the physical structure of the data.Popular Database Models Hierarchical Database Network Database Relational Database - most popular

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Relational DatabaseA logical representation of the data that allows the relationships between the data to be considered without concerning oneself with the physical implementation of the data structures.

Codd, 1988Composed of tables

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TablesRelated data divided up into fields (columns) and records (rows)

Should contain a Primary Key An identifier that is unique to each

record Examples include SSN, Vehicle ID #’s,

Employee ID #’s, Course #’s, Reference #’s. Usually are associated with an ordering

Ascending or Descending

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Example

CourseNo RefNo Instructor CampusCGS1100 15689 McManus DLCGS1100 15690 McManus FWBCGS1100 15692 McManus FWBCGS1100 15693 McManus FWBCGS1570 15706 McManus FWBCGS1570 15707 McManus DLCIS1000 15735 McManus DLCOP2011 17055 McManus NicevilleCOP2010 17056 McManus Niceville

Records

Fields

Primary Key

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Projections & JoinsProjection Selecting a subset of fields from a set

of records Filters and Queries

Join Combining selected fields from multiple

tables. Queries

Both are accomplished through SQL.

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Advantages over Hierarchical & Network Schemes1. Tabular representation is easier for

users to understand and easier to implement in the physical database system.

2. Easy to convert other database structures into a relational scheme.

3. Projection and join operations are easy to implement and make the creation of new tables easy.

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Advantages cont.4. Searches are generally faster than

when using schemes that use pointers.5. Relational structures are easier to

modify.Advantage when flexibility is an issue.

6. Database clarity and visibility.Tabular format is easier for the user to search than when using more complex structures.

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Primary KeysUniquely identifies each record in the table. Rule of Entity Integrity

Every record must have a value in the primary key field

The value must be unique Duplicates -- not allowed

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Foreign KeysA field in a table for which every entry has a unique value in another table and where the field in the other table is the primary key for that table. Rule of Referential Integrity

every value in a foreign key field must appear in another table’s primary key field

Provide the means of joining multiple tables

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SQL Query KeywordsSQL Keyword Description

SELECT Selects (retrieves fields from one or more tables

FROMSpecifies tables from which to get fields or delete records. Required in every SELECT and DELETE statement.

WHERE Specifies criteria that determines the rows to be retrieved

INNER JOINJoins records from multiple tables to produce a single set of records

GROUP BY Specifies criteria for grouping records

ORDER BY Specifies criteria for ordering records

INSERT Inserts data into a specified table

UPDATE Updates data in a specified table

DELETE Deletes data from a specified table

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SQL CommandsSELECT Chooses information from one or more

tables in a database.

SELECT * FROM TableName

The * indicates that all fields from TableName should be selected

SELECT Au_ID, LastName FROM Authors

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SQL CommandsWHERE Clause Provides the selection criteria

Records must match the criteria in order to be selected

SELECT * FROM Authors WHERE [Year Born] >= 1950SELECT * FROM Authors WHERE Author Like ‘d[a-e]*’

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SQL CommandsORDER BY Clause Query results are sorted in either

ascending or descending order

SELECT * FROM Authors ORDER BY Author ASC

SELECT authorID, firstName, lastNameFROM AuthorsORDER BY lastName, firstName ASC

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SQL CommandsINNER JOIN Merges Data from Multiple Tables

SELECT * FROM Authors INNER JOIN [Title Author] ONAuthors.Au_ID = [Title Author].Au_ID

The dot notation is necessary when the same field exists in two separate tables.

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SQL CommandsINSERT Inserts a new record in a table

INSERT INTO tableName (field1, field2, …, fieldNameN )VALUES (value1, value2, …, valueN )

INSERT INTO Authors ( firstName, lastName )VALUES (‘Sue’, ‘Smith’ )

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SQL CommandsUPDATE Modifies data in a table

UPDATE tableName SET field1 = value1, field2 = value2, …, fieldN = valueNWHERE criteria

UPDATE Authors SET lastName = ‘Jones’WHERE lastName = ‘Smith’ AND firstName = ‘Sue’

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SQL CommandsDELETE Removes data from a table

DELETE FROM tableName WHERE criteria

DELETE FROM AuthorsWHERE lastName = ‘Jones’ AND firstName = ‘Sue’

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Biblio.mdb Predefined Query

SELECT Titles.Title, Titles.ISBN, Authors.Author,Titles.[Year Published], Publishers.[Company

Name]FROM

Publishers INNER JOIN (Authors INNER JOIN ([Title Author] INNER JOIN Titles ON [Title Author].ISBN = Titles.ISBN) ON Authors.Au_ID = [Title Author].Au_ID)ON Publishers.PubID = Titles.PubIDORDER BY Titles.Title

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ADO.Net

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ADO.Net Data Objects

SelectCommand

InsertCommand

UpdateCommand

DeleteCommand

DataAdapter DataSet

Data Tables

DataTable DataTable

Data Rows Data Rows

Data Columns

Data Columns

Data Relations

Your Code

Database

Connection

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