VB.NET tutorial: Command and DataReader Objects

ADO.NET

Command and DataReader Objects

To be able to work with data of the database, it is important to gain basic knowledge of SQL language. In this part, we introduce you the basic sql statements commonly used. In this instruction, we use Tablename to refer to the table and fieldname to refer to the field of the table that we will work with.

Retrieve data from a table

SELECT * FROM Tablename;
Example:
SELECT * FROM Products;

Retrieve data from a table with sorting

SELECT * FROM Tablename
Order by fieldname Asc/Desc;

Example:
SELECT * FROM Products
Order By ProductID DESC;

Retrieve data from a table with condition

SELECT * FROM Tablename
Where condition;

Example:
SELECT * FROM Products
Where UnitPrice Between 20 And 30;
SELECT * FROM Products
Where UnitPrice>20 And UnitsOnOrder>20;

Retrieve data from multiple tables

SELECT Tablename1.fieldname1, Tablename1.fieldname2, Tablename2.fieldname1,
Tablename2.fieldname2
FROM Tablename1, Tablename2
Where how these tables are related

Example:
SELECT Products.ProductName,Products.UnitPrice,Products.UnitsInStock, Categories.CategoryName
FROM Products,Categories
Where Products.CategoryID=Categories.CategoryID;

Insert data into a table

INSERT INTO Tablename Values(val1,val2,value3..)

Example:
INSERT INTO Student_tbl Values('Stu006','Rithy Vansak');

Insert data into a table by specifying field names

INSERT INTO Tablename(fieldname1, fieldname 2,..)
Values(val1,val2,value3..)
Example:
INSERT INTO Student_tbl(StuID,StuName) Values('Stu007','Rithy Vansak');

Update data in a table

UPDATE TableName
SET fieldname 1=val1, fieldname 2=val2,f2…
Where condition
Example: UPDATE Student_tbl Set StuName='Rithy Chan'
Where StudID='Stu007';

Delete data from a table

-DELETE FROM Tblname Where condition;
Example:
DELETE FROM Student WHERE StuID='Stu007' Note: For DELETE and UPDATE statements, you should set conditions(s). If you don’t set condition(s), all of your data in a specified table will be deleted or updated.

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Posted comments

Phan Neth, CICI, year 3:

Now it is ok teacher. I can connect to database and select data from it. Than you so much teacher !!!!!

04-30-2013

Dara:

Copy and paste the link below to the address box to learn how to connect C and Mysql server:
http://www.worldbestlearningcenter.com/index_files/cpp-tutorial-connect_mysql_database.htm

04-27-2013

Phan Neth, CICI, year 3:

Hello teacher i want to connect C programming language to MySql server but it have problem. When i compile it always error with library " my_global.h
and mysql.h", so how should i do?

04-27-2013

Phan Neth, Year 3 at CICI,:

I have some problem about connection to mysql server. So I hope teacher can help me. Thank !!!!

04-26-2013

Federico:

Output appears the same also this way:

static void Main(string[] args)
{
int[,] myArray = new int[5, 5];
int row, i;
int n = 1;

for (row = 0; row < 5; row++)
{
for (i = 0; i < 5; i++)
{
myArray[row, i] = n;
if (row == 1 && i == 2) Console.Write(" \t");
else Console.Write("{0} \t", n);

if (n!=26) n++;
if((i+1)%5==0) Console.WriteLine("\n");
}
}
Console.ReadLine();
}

04-13-2013

Dara:

Let pointer p point to the index 1 elem (value=2) of the array.
int *p= a+1;
Let pointer q point to the index 6 elem (value=5) of the array.
int *q= a+6;
-Expression q-p is the subtraction of address of the index 6 element and the address of index 1 elem of the array. So, the result is 5.
-Expression *p+*q is the sum of the value of index 1 elem (2) and the value of index 6 elem (5). So, the result is 7.
In conclusion, the output is 57.

03-28-2013

Anushka :

Find the output of following code
main()
{
int a[] = {1,2,9,8,6,3,5,7,8,9};
int *p= a+1; int *q= a+6;
cout<< q-p <<*p+*q; }

03-28-2013

Dara:

Option Explicit
Dim Cn as New ADODB.Connection
Private Sub_Form_Load()
Cn.Open "Provider=SQLOLEDB; Data Source=ServerName; Initial Catalog=DatabaseName;UserID=UserName; Password=Passw"
End Sub
You will need to replace ServerName with the name of your server (installed SQL Server), DatabaseName withe the name of your data file that you want to connect to, UserName with the name of the user to login to SQL Server, and Passw with the password used to login to SQL Server.

03-13-2013

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VB.NET tutorial: Command and DataReader Objects

ADO.NET

Command and DataReader Objects

Retrieve data from a table

Retrieve data from a table with sorting

Retrieve data from a table with condition

Retrieve data from multiple tables

Insert data into a table

Insert data into a table by specifying field names

Update data in a table

Delete data from a table

VB.NET programming tutorial

Posted comments