What is difference between unique key and primary key?

There is two difference between them.

1. The not null constraint is by default added to primary key, it means, primary key attribute cannot accept null values, whereas, the attribute declared as unique can accept null values. It is the major difference between the two.

2. Secondly, we can have only one primary key in a relation, whereas, multiple attributes can be declared unique at the same time.

Binding Checked List box control with data

        CheckedListAccount.DataSource = Dset.Tables(0) ' Dataset containing datatable

        CheckedListAccount.DisplayMember = "account_name" 'display field
        CheckedListAccount.ValueMember = "account_id"        'id filed

'to get selected items id from checked list box


        For Each checkeditem As DataRowView In CheckedListAccount.CheckedItems
            MsgBox(checkeditem.Item("account_id").ToString())
        Next

In SQL, what are the differences between primary, foreign, and unique keys?

Both primary and unique keys can span multiple columns within a table. Two differences exist: 1. A table may have more than one unique key. This depends on the design of the table. But, a table can have only one primary key. 2. The values in the unique key columns may or may not be NULL. The values in primary key columns, however, can not be NULL. While unique and primary keys both enforce uniqueness on the columns of one table, foreign keys define a relationship between 2 tables. A foreign key identifies a column or group of columns in one (referencing) table that refers to a column or group of columns in another (referenced) table. Both unique and primary keys can be referenced by foreign keys.

What is the difference between SMALLDATETIME and DATETIME?

"What's that", you ask? You never heard of this SmallDateTime data type?

That does not change the fact that it does indeed exist. And yes, even your SQL Server 2000 has it!

Here are the main differences you should know about these two datetime types:

1. Range of Dates

A DateTime can range from January 1, 1753 to December 31, 9999.
A SmallDateTime can range from January 1, 1900 to June 6, 2079.

2. Accuracy

DateTime is accurate to three-hundredths of a second.
SmallDateTime is accurate to one minute.

3. Size

DateTime takes up 8 bytes of storage space.
SmallDateTime takes up 4 bytes of storage space.


Armed with this knowledge, you may want to use SmallDateTime instead of DateTime if you only need to represent dates from January 1, 1900 to June 6, 2079 and you do not need accuracy below 1 minute. Why? Simple! Using SmallDateTime will reduce the amount of data your queries are pulling back. The size of each row will be a bit smaller.


That's it for now... be sure to check back soon for more information on using datetime in SQL Server.

Search column name in tables in SQL Database

select
sc.name as col_name,so.name as table_name from syscolumns sc inner join sysobjects so on so.id=sc.id where sc.name like 'column_name' and so.xtype='U'

To convert any date filed with time to date without time like 1-Jan-2012 00:00:00.00

update TableName set Datefield=cast(convert(varchar,datefield,106) as datetime)

Save VsFlexGrid data to excel

1. Private Sub FlexToExcel()
2. Dim xlObject    As Excel.Application
3. Dim xlWB        As Excel.Workbook
4.        
5.     Set xlObject = New Excel.Application
7.     'This Adds a new woorkbook, you could open the workbook from file also
8.     Set xlWB = xlObject.Workbooks.Add
9.                
10.     Clipboard.Clear 'Clear the Clipboard
11.     With MSFlexGrid1
12.         'Select Full Contents (You could also select partial content)
13.         .Col = 0               'From first column
14.         .Row = 0               'From first Row (header)
15.         .ColSel = .Cols - 1    'Select all columns
16.         .RowSel = .Rows - 1    'Select all rows
17.         Clipboard.SetText .Clip 'Send to Clipboard
18.     End With
19.            
20.     With xlObject.ActiveWorkbook.ActiveSheet
21.         .Range("A1").Select 'Select Cell A1 (will paste from here, to different cells)
22.         .Paste              'Paste clipboard contents
23.     End With
24.    
25.     ' This makes Excel visible
26.     xlObject.Visible = True
27. End Sub

Binding Combobox at run time without using database connection via Dictionery Objec

        Dim objDict As New Dictionary(Of String, String)
        objDict.Add("1", "Value 1")
        objDict.Add("2", "Value 2")


        ComboBox1.DataSource = New BindingSource(objDict, Nothing)
        ComboBox1.DisplayMember = "Value"
        ComboBox1.ValueMember = "Key"

Difference between Panel and GroupBox classes in .NET

The both classes that is Panel and GroupBox can be used as a container for other controls such as check box control, radio button control etc. But the difference between these two classes is 
• In case of Panel class captions cannot be displayed i.e. we can’t set caption but in GroupBox class captions can be displayed. 
• The Panel class can have scroll bars but GroupBox class cannot have scroll bar.

Add row to bound Datagrideview

        Dim dr As DataRow = CType(DgviewDetail.DataSource, DataTable).NewRow
        dr.Item(1) = "anand"

        'DgviewDetail.Rows.Add(dr)

        CType(DgviewDetail.DataSource, DataTable).Rows.Add(dr)

excel connection string

ExcelCon = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + WorkBook + ";Extended Properties='Excel 8.0;HDR=YES;IMEX=1;';")

to set database owner

use databasename

sp_changedbowner

user_name

access connection string with password and without password
  
    If DbPass.Length > 0 Then
            AccCon = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Jet OLEDB:Database password=" & DbPass & ";Data Source=" & Dpath & "")
        Else
            AccCon = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Persist Security Info=False;Data Source=" & Dpath & "")
        End If

Tech

if you want to re install visual studio on your pc then use control panel add/remove option