Question

I’m new to the SQL query language and I’m trying to figure out how to delete a row (in a SQL DB table) with a non key ID column value using vb.net. For example in the table TEST below:

ID     Name 
1      x 
2      y 
3      z

I have a windows form that the user selects the Name value, however when I run my code it says

Cannot convert varchar “y” to int.

Here is my code attempt:

Dim sConnectionString As String

sConnectionString = "Data Source=" + serverName + ";Initial Catalog=" + dbName + ";Integrated Security=SSPI;"

Dim objConn As New SqlConnection(sConnectionString)
objConn.Open()

Dim cmd As New SqlCommand

cmd.Connection = objConn
cmd.CommandText = "DELETE FROM TEST WHERE Name = y"

cmd.ExecuteNonQuery()

Thank you!

Answer 1

If your Name column is of type varchar you need to enclose the value in single quotes

cmd.CommandText = "DELETE FROM TEST WHERE Name = 'y'" 

A complete answer to your question will be:

Dim sConnectionString As String 
sConnectionString = "Data Source=" + serverName + _
                     ";Initial Catalog=" + dbName + _ 
                     ";Integrated Security=SSPI;" 

Dim objConn As SqlConnection
Using(objConn = new SqlConnection(sConnectionString) 
    objConn.Open() 
    Dim cmd As New SqlCommand 
    cmd.Connection = objConn 
    cmd.CommandText = "DELETE FROM TEST WHERE Name = @name" 
    cmd.Parameters.AddWithValue("@name", txtName.Text)
    cmd.ExecuteNonQuery() 
End Using

I’m supposing that your user insert the name to delete in a textbox and you pass this value to a parametrized query. The use of parametrized query will save you from the hassle to handle quoting problems and from Sql Injection Attacks