ASP.NET 2.0

Chapter 7Managing Data Sources

Objectives

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Working with Database Applications

Data can be stored and formatted using a variety of tools and technologies

A relational database management system (RDBMS) is a system that stores data in related tables An RDBMS may contain additional tools to

help create and manage tables, and provide an interface for programmers to develop applications that can communicate with the database

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Characteristics of a Relational Database

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Relationships Between Tables

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Relationships Between Tables (continued)

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Applications That Store Relational Data

There are three examples of popular relational databases Microsoft Access

Microsoft Access stores the information in a single file and can only handle a few concurrent connections through the web, and is less secure than SQL Server

Microsoft SQL Server Microsoft SQL Server is a robust database application

that also allows you to create stored procedures and supports transactions

Oracle Oracle databases commonly are used with web

applications built with Java and PHP technologies

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Visual Studio .NET Built-in Database Tools

A variety of Visual Studio .NET tools allow you to create and manipulate a database With these tools, you can create the database

from scratch or convert the data from an existing format into a relational database

You can also import data from a spreadsheet into a Microsoft Access database

In addition, you can convert a Microsoft Access database to a SQL Server database

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Creating a SQL Server Database in Visual Studio .NET

Visual Studio .NET provides a graphical user interface that you can use to create a connection to a database

When you create the database, you need to know the type of authentication required for access to the SQL Server You can use the authentication built within Windows NT,

or SQL Server authentication You can create the database in either the Database

Explorer window or the Solution Explorer window If you create the database in the App_Data folder in the

Solution Explorer window, then both the SQL Server data file and the transaction log are stored in the App_Data folder This database can be easily moved by simply

detaching the database from this instance of SQL Server and reattach it to another instance of SQL Server

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Using the Table Designer

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Using the Table Designer (continued)

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Using the Table Designer (continued)

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Creating a Relationship with the Database Diagram

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Views and Queries

TheVisual Studio .NET SQL Editor is used to create and edit views, SQL scripts, and stored procedures

Views and queries allow you to retrieve information from the database Queries are SQL commands that retrieve data

from the database SQL scripts and stored procedures may

contain the same SQL commands used in queries and views

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Using Views and Queries

Queries and views can both be used to retrieve data A view is an SQL statement that is saved with the

database as part of a database design Views can contain only select statements, which means

that views can retrieve data; they cannot be used to create, update, or delete data

View Designer is used to create and manage views and works only with SQL Server

A query is an SQL statement that is saved with a Visual Studio database project and not with the database The Query Designer can be used to create, update, and

delete data

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Building a View with the Query and View Designer

The Query and View Designer allows you to create a query or view within Visual Studio .NET

To aid you in creating views and queries, there are four windows called panes displayed within the Query and View Designer Diagram Pane Grid Pane SQL Pane Results Pane

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SQL Statements

You can build and modify the SQL commands to retrieve a select group of records

To retrieve all the records in the Products table, you can use this SQL command: SELECT * FROM Products

The keyword FROM is used to indicate the name of the table where the data is retrieved

You can retrieve the list of manufacturers by using the Select statement: SELECT DISTINCT Manufacturers FROM Products

The view can use the keyword TOP to retrieve a subset of the records in the table: SELECT TOP (50) PERCENT * FROM Products

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Creating Search Conditions

You can use keywords to qualify a subset of records and columns to retrieve

The WHERE clause of a search condition consists of the keyword WHERE, an expression, a comparison operator, and another expression Valid comparison operators include +, <, >, <>, IS, and

ISNOT Example: WHERE Member='Staff' AND Salary>55000

The GROUP BY clause allows you to aggregate the records based on the values of one of the columns Example: SELECT *FROM Products GROUP BY

CategoryID The JOIN clause allows you to combine one or more

tables into a single set of recordsASP.NET 2.0, Third Edition 18

Mondial Database

“of whole world: relating to or involving the entire world” (Encarta)

SQL Server file on web site in recordings directory

http://www.dbis.informatik.uni-goettingen.de/Mondial/

Various sources of country data

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Some Views Of Mondial

Country-City Country-Ethnic Country-Language

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SQL Stored Procedures and SQL Server Scripts

Stored procedures can be used to create an SQL command that is stored within the database The stored procedure is more efficient than an

SQL statement because it is precompiled by the server

Stored procedures are created within Visual Studio .NET

SQL Server scripts provide you with the ability to store SQL commands in an external text file SQL Server scripts are often used to create

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Input and Output Parameters

A stored procedure can be used to run a SQL statement

A good technique is to pass values to the stored procedure that can be used in the SQL statement The name of any parameter within a stored procedure

always begins with the @ symbol An input parameter is a value that is passed to the

stored procedure when it is called The data type and length of this value must match

the data type and length that is specified within the stored procedure

Output parameters can send values back to the object that called the stored procedure

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The Return Code

You can have a return value passed back to the stored procedure call

The return code is indicated with the keyword RETURN and is often used to indicate the status of the query By default, the return value is set to 0, which

means the query execution was successful When the value is 1, the required parameter

value was not passed to the query When the value is 2, the parameter passed

was not valid

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Modifying a Stored Procedure with the SQL Editor

The SQL Query Builder has the same user interface as the Query and View Editor

The code to create the query, however, is stored in the stored procedure

Within the stored procedure, you can edit the blocks of code that are enclosed within a blue line, via the SQL Query Builder You only need to right-click the block and

select Design SQL Block

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Using Built-In Views and Stored Procedures

Built-in views and stored procedures allow you to retrieve information about your database The sp_tables built-in stored procedure would return a

list of tables in the database The sp_columns built-in stored procedure would return

the list of columns for the name of the table that is passed as a parameter to the stored procedure

You can access the stored system views and stored procedures in the Database Explorer

It is important to provide strong security for the SQL server, because some of the built-in stored procedures can be used maliciously if your SQL Server security has been breached

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Database Connections

In order to create a connection to databases, one must know: The parts of a connection string How to store a connection string in the web

configuration file How to create a connection to the database

from a web page How to move data from Access to SQL Server

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Understanding the Connection String

The connection string is a piece of text that contains the location of your database and any additional information required to access the database

The connection string format is different for each database because each database has different connection string requirements When you use Visual Studio .NET to create a connection

to a database, you will fill out the connection information using a dialog box, and the software will create the connection string for you

The following code is a sample of a connection string to a SQL Server database: Data Source=.\SQLEXPRESS; AttachDbFilename="C:\

[Yourfolder]\Chapter7\App_Data\Chapter7.mdf”; Integrated Security=True;

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Storing Connection Strings in the Web Configuration File

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Storing Connection Strings in the Web Configuration File

(continued)

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Storing Connection Strings in the Web Configuration File

(continued)

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Creating a Connection to a Database

from a Web Page (continued)

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Creating a Connection to a Database

from a Web Page (continued)

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Creating a Connection to a Microsoft Access Database

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Creating a Connection to a Microsoft Access Database (continued)

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Creating a Connection to XML Data

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Moving Data to SQL Server

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Summary Relational databases store data related tables. Tables

consist of rows and columns. When you create the column, you must identify the data type, the file size, and if the column allows, null values.

Relationships between tables are defined in the Database Diagram. The primary key column contains a unique value for each row of data and is used to create the relationship in other tables. When values of primary keys are stored in other tables, they are called foreign keys.

Normalization is the process used to design databases, which will reduce redundancy, promote data integrity, and improve database performance.

You can use the Visual Database Tools within Visual Studio .NET to create and maintain your databases.

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Summary (continued) The Table Designer allows you to create tables and enter

data.

The Query and View Designer allows you to create queries called views. Views are stored in the database and only are used with select statements. Queries must be executed manually but can contain INSERT, UPDATE, and DELETE statements.

The SQL Editor allows you to create stored procedures. Stored procedures are SQL commands that are stored with the SQL Server, and then compiled. Therefore, stored procedures run faster than SQL commands that are stored on a web page.

The SQL Query Builder allows you to use the visual tools to build your stored procedures. SQL Server scripts are files that contain SQL statements and are often used to create new databases and backup existing databases.

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Summary (continued) You can store the connection strings in the root level

Web.config application configuration file making them available from any web page in the application using global application variables or the connectionStrings element.

The connection string syntax varies with each type of database. The connection string contains the information needed to identify the type of database, the location of the database, the software provider required to communicate with the database, and user permissions required to access the data in the database.

You can convert a Microsoft Access database to SQL Server using the upsizing wizard. ASP.NET allows you to create connections to non-Microsoft data sources such as XML files.

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