CODEWITHSUNDEEP
c#sql-serverdelete-row
ikathegreat
ikathegreat

Reputation: 2321

Delete a row from a SQL Server table

I'm trying to simply delete a full row from my SQL Server database table using a button event. So far none of my attempts have succeeded. This is what I'm trying to do:

public static void deleteRow(string table, string columnName, string IDNumber)
{
    try
    {
    using (SqlConnection con = new SqlConnection(Global.connectionString))
    {
         con.Open();
         using (SqlCommand command = new SqlCommand("DELETE FROM " + table + " WHERE " + columnName + " = " + IDNumber, con))
         {
               command.ExecuteNonQuery();
         }
         con.Close();
    }
    }
    catch (SystemException ex)
       {
       MessageBox.Show(string.Format("An error occurred: {0}", ex.Message));
       }
    }
}

I keep receiving the error:

A first chance exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll An error occurred: Operand type clash: text is incompatible with int

All of the columns in the table are of TEXT type. Why cannot I compare the function argument of type string to the columns to find the match? (And then delete the row?)

Upvotes: 8

Views: 148472

Answers (8)

Barbi Angel Tupaz
Barbi Angel Tupaz

Reputation: 1

private void DeleteProductButton_Click(object sender, EventArgs e)
{


    string ProductID = deleteProductButton.Text;
    if (string.IsNullOrEmpty(ProductID))
    {
        MessageBox.Show("Please enter valid ProductID");
        deleteProductButton.Focus();
    }
    try
    {
        string SelectDelete = "Delete from Products where ProductID=" + deleteProductButton.Text;
        SqlCommand command = new SqlCommand(SelectDelete, Conn);
        command.CommandType = CommandType.Text;
        command.CommandTimeout = 15;

        DialogResult comfirmDelete = MessageBox.Show("Are you sure you want to delete this record?");
        if (comfirmDelete == DialogResult.No)
        {
            return;
        }
    }
    catch (Exception Ex)
    {
        MessageBox.Show(Ex.Message);

    }
}

Upvotes: 0

Miguel
Miguel

Reputation: 26

If you are using MySql Wamp. This code work.

string con="SERVER=localhost; user id=root; password=; database=dbname";
public void delete()
{
try
{
MySqlConnection connect = new MySqlConnection(con);
MySqlDataAdapter da = new MySqlDataAdapter();
connect.Open();
da.DeleteCommand = new MySqlCommand("DELETE FROM table WHERE ID='" + ID.Text + "'", connect);
da.DeleteCommand.ExecuteNonQuery();

MessageBox.Show("Successfully Deleted");
}
catch(Exception e)
{
MessageBox.Show(e.Message);
}
}

Upvotes: 0

robin
robin

Reputation: 21

private void button4_Click(object sender, EventArgs e)
{
    String st = "DELETE FROM supplier WHERE supplier_id =" + textBox1.Text;

    SqlCommand sqlcom = new SqlCommand(st, myConnection);
    try
    {
        sqlcom.ExecuteNonQuery();
        MessageBox.Show("delete successful");
    }
    catch (SqlException ex)
    {
        MessageBox.Show(ex.Message);
    }
}



private void button6_Click(object sender, EventArgs e)
{
    String st = "SELECT * FROM suppliers";

    SqlCommand sqlcom = new SqlCommand(st, myConnection);
    try
    {
        sqlcom.ExecuteNonQuery();
        SqlDataReader reader = sqlcom.ExecuteReader();
        DataTable datatable = new DataTable();
        datatable.Load(reader);
        dataGridView1.DataSource = datatable;
    }
    catch (SqlException ex)
    {
        MessageBox.Show(ex.Message);
    }
}

Upvotes: 0

user1082916
user1082916

Reputation:

As you have stated that all column names are of TEXT type, So, there is need to use IDNumber as Text by using single quote around IDNumber.....

    public static void deleteRow(string table, string columnName, string IDNumber)
    {
    try
    {
    using (SqlConnection con = new SqlConnection(Global.connectionString))
    {
         con.Open();
         using (SqlCommand command = new SqlCommand("DELETE FROM " + table + " WHERE " + columnName + " = '" + IDNumber+"'", con))
         {
               command.ExecuteNonQuery();
         }
         con.Close();
    }
    }
    catch (SystemException ex)
       {
       MessageBox.Show(string.Format("An error occurred: {0}", ex.Message));
       }
    }
 }

Upvotes: 20

lmatt
lmatt

Reputation: 197

You may change the "columnName" type from TEXT to VARCHAR(MAX). TEXT column can't be used with "=".
see this topic

Upvotes: 1

Ali
Ali

Reputation: 3615

Try with paramter

.....................
.....................

    using (SqlCommand command = new SqlCommand("DELETE FROM " + table + " WHERE " + columnName + " = " + @IDNumber, con))
             {
                   command.Paramter.Add("@IDNumber",IDNumber)
                   command.ExecuteNonQuery();
             }

.....................
.....................

No need to close connection in using statement

Upvotes: 5

sam yi
sam yi

Reputation: 4934

Looks like IDNumber is a string. It needs single quote wrapped around it.

"DELETE FROM " + table + " WHERE " + columnName + " = '" + IDNumber + "'"

Upvotes: 1

user27414
user27414

Reputation:

Either IDNumber should be an int instead of a string, or if it's really a string, add quotes.

Better yet, use parameters.

Upvotes: 6

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