.

Sunday, September 16, 2018

Difference between TRUNCATE and DELETE in SQL Server?

TRUNCATE:

It is a DDL command
It does not support WHERE clause/condition
Removes all the data all the time
Faster than DELETE as it locks entire table
It removes the data by deallocating the data pages used to store the table’s data, and only the page deallocations are recorded in the transaction log It does not activate triggers
Table identity column is reset to seed value

Syntax:

TRUNCATE TABLE TableName

DELETE:

It is DML command
It supports WHERE clause/condition
Removes data based on conditions specified in the WHERE clause (removes all the data if there is no WHERE clause) Slower than TRUNCATE as it takes row level locks
It removes rows one at a time and records an entry in the transaction log for each deleted row
It does activate triggers
Table identity column is not reset

Syntax:

DELETE FROM TableName WHERE ColName = ‘YourCondition’

Note

Truncate and Delete both are logged operations and both can be rolled back when they are within transactions. It is myth that Truncate is not logged operations. It is indeed logged operations and it locks page level deallocations.

Fundamentals of Garbage Collection

In the common language runtime (CLR), the garbage collector serves as an automatic memory manager. It provides the following benefits:

Enables you to develop your application without having to free memory.
Allocates objects on the managed heap efficiently.
Reclaims objects that are no longer being used, clears their memory, and keeps the memory available for future allocations. Managed objects automatically get clean content to start with, so their constructors do not have to initialize every data field.
Provides memory safety by making sure that an object cannot use the content of another object.

Click here to read full article by Microsoft

Wednesday, February 8, 2012

Creating Hit Counter for Total Page Views

In Count.aspx
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Label ID="lblCounter" runat="server"></asp:Label>

    </div>
    </form>
</body>

In Count.aspx.cs

protected void Page_Load(object sender, EventArgs e)
    {
        this.countMe();

        DataSet tmpDs = new DataSet();
        tmpDs.ReadXml(Server.MapPath("~/counter.xml"));

        lblCounter.Text = tmpDs.Tables[0].Rows[0]["hits"].ToString();
      // application["activeuser"] = application["activeuser"] + 1;
    }
    private void countMe()
    {

        DataSet tmpDs = new DataSet();
        tmpDs.ReadXml(Server.MapPath("~/counter.xml"));

        int hits = Int32.Parse(tmpDs.Tables[0].Rows[0]["hits"].ToString());

        hits += 1;

        tmpDs.Tables[0].Rows[0]["hits"] = hits.ToString();

        tmpDs.WriteXml(Server.MapPath("~/counter.xml"));

    }

In counter.xml/
<?xml version="1.0" standalone="yes"?>
<counter>
<count>
    <hits>0</hits>
</count>
</counter>

Sunday, January 8, 2012

Get Stored Procedure Return Value

SqlConnection con = null;
        try
        {
            string connString = ConfigurationManager.ConnectionStrings["cnTest"].ConnectionString;
            con = new SqlConnection(connString);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = "usp_ValidateUser";
            cmd.Parameters.AddWithValue("@Name", txt1.Text);
            con.Open();
            // Return value as parameter
            SqlParameter returnValue = new SqlParameter("returnVal", SqlDbType.Int);
            returnValue.Direction = ParameterDirection.ReturnValue;
            cmd.Parameters.Add(returnValue);

            // Execute the stored procedure

            cmd.ExecuteNonQuery();
            con.Close();

            Int32 ret= Convert.ToInt32(returnValue.Value);
            Response.Write(Convert.ToString(ret));

        }
        catch (SqlException ex)
        {
            // handle error
        }
        catch (Exception ex)
        {
            // handle error
        }
        finally
        {
            con.Close();
        }

Create Proc usp_ValidateUser
@Name Varchar(50)
AS
BEGIN
        if exists(Select Name from tblTestUser where Name=@Name)
        Begin
                return 1
        End

        else
         Begin
                return -1
        End


END

Get selected index, value,text of ASP.Net drop down list in javascript

<%-- In Head section--%>
<script type="text/javascript" language="javascript">

            function getDropdownListValues() {
            var DropdownList = document.getElementById('<%=aspdropdown.ClientID %>');
            var SelectedIndex = DropdownList.selectedIndex;
            var SelectedValue = DropdownList.value;
            var SelectedText = DropdownList.options[DropdownList.selectedIndex].text;

            var LabelDropdownList = document.getElementById('<%=lblDropdownList.ClientID %>');
            var sValue = 'Index: ' + SelectedIndex + '<br/> Selected Value: ' + SelectedValue + '<br/> Selected Text: ' + SelectedText;

            LabelDropdownList.innerHTML = sValue;
        }
    </script>

<%-- In body section--%>

<div>
        <asp:Label runat="server" ID="lblText">Asp.net DropdownList</asp:Label><br />

        <asp:DropDownList ID="aspdropdown" runat="server" onchange="getDropdownListValues();">
            <asp:ListItem Value="Test1" Text="Testing1"></asp:ListItem>
            <asp:ListItem Value="Test2" Text="Testing2"></asp:ListItem>
            <asp:ListItem Value="Test3" Text="Testing3"></asp:ListItem>
            <asp:ListItem Value="Test4" Text="Testing4"></asp:ListItem>
            <asp:ListItem Value="Test5" Text="Testing5"></asp:ListItem>
        </asp:DropDownList> <br />

        <asp:Label runat="server" ID="lblDropdownList"></asp:Label>
    </div>

Friday, January 6, 2012

HTML To PDF Converter Asp.net

using Pdfizer; //download Pdfizer and itextsharp dll also
using System.IO;

protected void btnDownload_Click1(object sender, EventArgs e)
    {
        string sPathToWritePdfTo = Server.MapPath(".") + "\\test.pdf";
        string path = Server.MapPath("./images/logo3w.png");
        System.Text.StringBuilder sbHtml = new System.Text.StringBuilder();
        sbHtml.Append("<html>");
        sbHtml.Append("<head>");
        sbHtml.Append("</head>");
        sbHtml.Append("<body>");
        sbHtml.Append("<div>");
        sbHtml.Append("<img src='" + path + "' alt='' />");
        sbHtml.Append("</div>");
        sbHtml.Append("<br/>");
        sbHtml.Append("<table border='0' cellpadding='0' cellspacing='0'>");
        sbHtml.Append("<tr><td>testing the text</td></tr>");
        sbHtml.Append("</table>");
        sbHtml.Append("</body>");
        sbHtml.Append("</html>");

        using (System.IO.Stream stream = new System.IO.FileStream
        (sPathToWritePdfTo, System.IO.FileMode.OpenOrCreate))
        {
            Pdfizer.HtmlToPdfConverter htmlToPdf = new Pdfizer.HtmlToPdfConverter();
            htmlToPdf.Open(stream);
            htmlToPdf.Run(sbHtml.ToString());
            htmlToPdf.Close();
        }
        System.Web.HttpContext.Current.Response.Clear();
        System.Web.HttpContext.Current.Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", "devtesting.pdf"));
        System.Web.HttpContext.Current.Response.ContentType = "application/pdf";
        System.Web.HttpContext.Current.Response.WriteFile(sPathToWritePdfTo);
        System.Web.HttpContext.Current.Response.End();
    }

/*http://itextpdf.com/terms-of-use*/

Wednesday, January 4, 2012

Export To CSV using ASP

<%
sub Write_CSV_From_Recordset( RS )

    '
    ' This sub-routine Response.Writes the content of an ADODB.RECORDSET in CSV format
    ' The function closely follows the recommendations described in RFC 4180:
    ' Common Format and MIME Type for Comma-Separated Values (CSV) Files
    ' http://tools.ietf.org/html/rfc4180
    '
    ' @RS: A reference to an open ADODB.RECORDSET object
    '

    if RS.EOF then

      '
      ' There is no data to be written
      '
      exit sub

    end if

    dim RX
    set RX = new RegExp
        RX.Pattern = "\r|\n|,|"""

    dim i
    dim Field
    dim Separator

    '
    ' Writing the header row (header row contains field names)
    '

    Separator = ""
    for i = 0 to RS.Fields.Count - 1
      Field = RS.Fields( i ).Name
      if RX.Test( Field ) then
        '
        ' According to recommendations:
        ' - Fields that contain CR/LF, Comma or Double-quote should be enclosed in double-quotes
        ' - Double-quote itself must be escaped by preceeding with another double-quote
        '
        Field = """" & Replace( Field, """", """""" ) & """"
      end if
      Response.Write Separator & Field
      Separator = ","
    next
    Response.Write vbNewLine

    '
    ' Writing the data rows
    '

    do until RS.EOF
      Separator = ""
      for i = 0 to RS.Fields.Count - 1
        '
        ' Note the concatenation with empty string below
        ' This assures that NULL values are converted to empty string
        '
        Field = RS.Fields( i ).Value & ""
        if RX.Test( Field ) then
          Field = """" & Replace( Field, """", """""" ) & """"
        end if
        Response.Write Separator & Field
        Separator = ","
      next
      Response.Write vbNewLine
      RS.MoveNext
    loop

end sub

'
' EXAMPLE USAGE
'
' - Open a RECORDSET object (forward-only, read-only recommended)
' - Send appropriate response headers
' - Call the function
'
    Set oConnection = Server.CreateObject("ADODB.Connection")
    oConnection.Open "Driver={SQL Server};Server=test123;Database=Test123;Uid=testsa;Pwd=test@123;"

    Set SQLStmt = Server.CreateObject("ADODB.Command")
    set rs=Server.CreateObject("ADODB.recordset")
    rs.Open "Select Id,Name as UserName from tblTestUser", oConnection

    dim RS1
    set RS1 = Server.CreateObject( "ADODB.RECORDSET" )
    RS1.Open "Select Id,Name as UserName from tblTestUser",oConnection
    Response.ContentType = "text/csv"
    Response.AddHeader "Content-Disposition", "attachment;filename=export.csv"
    Write_CSV_From_Recordset RS1
%>