How To Check If Data Already Exists In Database?

I was able to get this code to work but now I get a SQL error if you try to submit the same information twice. 
How can I add a message saying that the "email" already exists in database without the SQL error?

    protected void Button1_Click1(object sender, EventArgs e)
        SqlConnection conn =
            new SqlConnection("Data Source=TECATE;Initial Catalog=subscribe_mainSQL; User Id=maindb Password=123456; Integrated Security=SSPI");
        SqlCommand cmd = new SqlCommand("INSERT INTO [main] (, [userid], [fname], [lname], [degree]) VALUES (@email, @userid, @fname, @lname, @degree)", conn);
            cmd.Parameters.AddWithValue("@email", email.Text);
            cmd.Parameters.AddWithValue("@userid", uscid.Text);
            cmd.Parameters.AddWithValue("@fname", fname.Text);
            cmd.Parameters.AddWithValue("@lname", lname.Text);
            cmd.Parameters.AddWithValue("@degree", degree.SelectedItem.Value);

            int i = cmd.ExecuteNonQuery();


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Check If Value Exists In Database?


I'm wondering is there a command that I can use to check if a certain value exists in the database? Something that returns true or false perhaps?

SELECT * FROM Customers WHERE ID ='1'

Ok so that's simple, but how can I return a true or false if '1' is a value that exists in the db?


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For any Database like (MS Access, Oracle, MS SQL-Server,MySQL)..

Please help me.....

thank's in advance.......

Paresh Patel.

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Hi all,I am in the process of creating a page that checks to see if a particular user exists in the database and if it does then send to welcome.aspx if not then accessdenied.aspx.  The userid is requested from the query string.I have done some research and cannot find anything directly related, I have tried to add bits of code into what i think is the right place but I dont think what i am doing is correct. Can someone help and show me where my code is going wrong? Also is there a better/more efficient way to do what I am doing?Thanks in advance. default.aspx.csusing System;using System.Data;using System.Data.SqlClient;using System.Configuration;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Web.UI.HtmlControls;public partial class _Default : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        string UserID = Request.QueryString["uid"];        //string TransferPage;        if (UserID != null)                {            //initiate connection to db            SqlConnection objConnect = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["MyConnection"].ConnectionString);            string sql = "SELECT COUNT(*) FROM members WHERE UserID = '" + UserID + "'";            SqlCommand query = new SqlCommand(cmd, test);            int count = (int)query.ExecuteScalar();            int aantal = -1; // some default value if can't insert record            if (count == 0) // no existing record for username            {                Server.Transfer("accessdenied.aspx");            }            else            {                Session["UID"] = UserID;                Server.Transfer("welcome.aspx");                            }                    }        }} 

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Check If Record Exists

 I was wondering if someone can help.
 In what is the best way to check if a record exists if you are using an sql data reader?
For my application I need to display a button control (make it visible on the page) if a record is available after executing my sql select statement.
Mark :)

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Check If Record Exists

 Hello,I created the following SQL script to check if a record exists:IF (EXISTS (SELECT LevelName FROM dbo.by27_Levels WHERE LOWER(@LevelName) = LOWER(LevelName)))  Return (1)ELSE  Return (0)And I also found in a web page another solution:IF EXISTS(SELECT 1 FROM TABLENAME WHERE LevelName=@LevelName)  SELECT 1ELSE  SELECT 0- Which approach should I use?- Why "SELECT 1 FROM"?- And when should I use SELECT or RETURN?All I need is to know if the record exists ... nothing else.I will use this procedure on an ASP.NET 2.0 / C# web site.I am not sure if this important but anyway ...Thank You,Miguel

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How can I do this?

And if the only way to control this is to create a stored procedure. How do I write such a proc?

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I try to use the Cursor_status function but it always returns -3.
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If I PRINT Cursor_Status('local','crInv') before and after the DECLARE statement it always returns -3.
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Best regards,

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Is there is a piece for code ot sample code that can let me check if a file exists? Has any one done this before?


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This my first time using the link server to read the files directly from within SQL2005, so issues the following link:-

EXEC sp_addlinkedserver
@server = N'MYVFPSERVER', -- Your linked server name here
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After that i can open query and do the import issues, but how can check if the table exists before issues the query.

Best regards

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Can anyone tell me how to go about establishing if a particular view exists on a table?


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In SSIS, I need an easy way to see if a file exists, and if not wait for it until a timeout period expires. Here are the options I've discovered, along with the issues I've had:

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This was my first attempt. The task works great, BUT only detects when there is a change on the file. If the file already exists, it keeps waiting which is not the behavior I need.
b) The WMI Event Task

There is very sparce documentation on this event and how to write a WQL query. There are numerous examples of monitoring a folder and if any files appear, cause an event to happen. I need to detect for a specific file. I found maybe one example of this using "PartComponent" but wasn't able to get the sytax right to make it work for me. I also need to access a remote file share using a UNC path (e.g. \servernamepathfile.txt) which I could not get to work.
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I'm open to suggestions or ways to get options a) and b) to work for my needs.

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Hi, can someone tell me how to check if a file exists. If it exists then i want to continue with the process and if it fails then send a mail to me.

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Is there any way to check whether the login exists before creating login ?

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Basically, i am still relatively new to and SQL. And i have the following query.
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I need to check via our staff table, which people have had a skill entered for them. And then produce a report on who has not had a skill entered for them.
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If there is more information that i can give you to assist me, please ask me.
 You help would be greatly appreciated.

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