ADO.NET Data Access. Page 2 SQL When we interact with the datasource through ADO.NET we use the SQL language to retrieve,modify,update information

ADO.NET Data Access

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SQL

When we interact with the datasource through ADO.NET we use the SQL language to retrieve,modify,update information

Structured Query Language is a standard data access language used to interact with relational database

SQL Select Statement

Update Statement

Insert Statement

Delete Statement


SQL Select Statement

To retrieve one or more rows of data the select command is used

SELECT [columns] FROM [tables] WHERE [search_condition]ORDER BY [order_expression ASC | DESC]


Sample Select Statement

(eg) SELECT * FROM Authors (*) - retrieves all the columns from the table

The FROM clause identifies that the Author table is being used

There is no WHERE clause, means all the records will be retrieved

There is no ORDER BY clause, means the data’s are not sorted


Improving the Select Statement

SELECT lname,fname FROM Authors WHERE State =‘MI’ ORDER BY lname ASC

Only two columns are retrieved

WHERE Clause provides the restriction to a particular state

An ORDER BY clause sorts the lname alphabetically in ascending order


The WHERE clause

(eg)SELECT * FROM Sales WHERE ord_date<‘2000/01/01’ AND ord_date> ‘1987/01/01’

Multiple conditions can be combined using the AND keyword

Greater than and Less than comparisons can be made using <,> symbols


SQL Update Statement

Syntax:

Eg UPDATE Authors SET lname=‘Gowri’ WHERE id =‘101’

UPDATE [table] SET [update_epression] WHERE [search_condition]


SQL Insert Statement

Syntax

Eg INSERT INTO Authors (lname,fname) VALUES (‘John’,’Khan’)

INSERT INTO [table] ([column_list]) VALUES ([value_list])


The SQL Delete Statement

Syntax

Eg DELETE FROM Authors WHERE id=‘102

DELETE FROM [table] WHERE [search_condition]


Simple Data Access

To retrieve information with simple Data Access follow these steps

Create Connection,Command,DataReader objects

Use DataReader to retrieve information from the database and display it in a control in the webform

Close your connection

Send the page to the user.At this point all the connections have been closed


Importing Namespaces

Imports System.Data

Imports System.Data.OleDb

(OR) Imports System.Data.SqlClient


Creating a connection

The first step is to make a connection with the database

Specify a value for the ConnectionString property

This property defines all the information the computer needs to find the data source,log in and initial database


The Connection String

The ConnectionString is actually a series of distinct pieces of

information,separated by semicolons(;)

Provider –This refers to the name of the Provider which allows

communication between ADO.NET and database (SQLOLEDB is the

provider for SQL)

Data Source – This refers to the name of the server where the data

source is located;Server is on the same computer so localhost


The Connection String

Initial CataLog – It refers to the name of the initial database

User ID – Used to access the database ,sa refers to the system admin

account

Password - By default the ‘sa’ account does not have a password

ConnectionTimeout – It determines how long your code will wait in

seconds before generating an error if it cannot establish connection

default 15 seconds


SQl Server Integrated Authentication

With SQL Server Authentication

SQL Server maintains its own user account

With integrated authentication

SQL Server automatically uses the windows account information for the currently logged in user


Making the connnection


Defining a select command

The connection object a few basic properties that give the information about the connection

An SQL Statement that selects the information you want

(eg) SELECT * from Authors

A command object that executes the SQL statement

SqlDataAdapter adap=new SqlDataAdapter(“SELECT * from Author”,con)

A DataSet object to store the retrieved objects

(eg)DataSet ds=new DataSet()

Documents

ADO.NET Data Access. Page 2 SQL When we interact with the datasource through ADO.NET we use the SQL language to retrieve,modify,update information