Comparing textbox to a set number of rows in a database

Question

Hi
I'm wondering if anyone can help me with a litle problem. I got this code:
Dim con As New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\MyDatabase.accdb")
Dim cmd As OleDbCommand = New OleDbCommand("SELECT * FROM produced WHERE serie = '" & SerieTextBox.Text & "' AND where = '" & WhereLabel2.Text & "'", con)
con.Open()
Dim sdr As OleDbDataReader = cmd.ExecuteReader()
If (sdr.Read() = True) Then
MessageBox.Show("It exist in " & WhereLabel2.Text)
con.Close()
Exit Sub
Else
MessageBox.Show("It does not exist in " & WhereLabel2.Text)
con.Close()
Exit Sub
End if
This works perfectly :) The thing is, the produced table contains close to 90.000 rows (and growing), and there are no reason to compair the textbox to more than the last 1000 rows. Is there an easy way for me to that? I'm a bit worried about performance
if I leave it like this.
Any tips or help is much appreciated :)

Answer 1

Hello,
I am going to provide an example but highly recommend you step back and learn first how to work with SQL outside of Visual Studio then take time to learn the basics of working with VB.NET basics followed by working with data at a simple level.
In
the project on OneDrive I did the following
Separated the database operations into a code module, could had gone one step farther and placed the code into a class but wanted to keep it simple
In the code module mentioned above there are two functions, the first has hard coded values used which in this case validates the query works properly. Thinking from experience what I did is write the query in (for this example) MS-Access query editor,
does it work? Yes, move to a project, if not continue in MS-Access until it does.
Test in Visual Studio project
Now modify the code to accept replaceable parameters for the where conditions and test via values sent via TextBox controls from the user and while doing so it is prudent to test if they actually entered values in the TextBox controls.
There are little things to look at in the code, study both functions to see things like being cognitive in regards to cleaning up objects (not obvious that the 'Using' statements do clean up but they do) . There is no exception handling, for live work
you might consider this via a Try-Catch-Finally statement but was kept out to keep things simple.  
Code from project
Form code
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
If HardCodedTestDemo() Then
MessageBox.Show("Got some")
Else
MessageBox.Show("None")
End If
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
If Not String.IsNullOrWhiteSpace(txtContactTitle.Text) AndAlso Not String.IsNullOrWhiteSpace(txtCountry.Text) Then
If RealDemo(txtContactTitle.Text, txtCountry.Text) Then
MessageBox.Show("Got some")
Else
MessageBox.Show("None")
End If
Else
MessageBox.Show("Please enter both title and country")
End If
End Sub
End Class
Code  module
Module DatabaseOperations
Private Builder As New OleDbConnectionStringBuilder With
.Provider = "Microsoft.ACE.OLEDB.12.0",
.DataSource = IO.Path.Combine(Application.StartupPath, "Database1.accdb")
''' <summary>
''' Here we have provided hard coded values known to exists for the where conditions
''' so that we know it works.
''' </summary>
''' <returns></returns>
''' <remarks></remarks>
Public Function HardCodedTestDemo() As Boolean
Using cn As New OleDbConnection With
.ConnectionString = Builder.ConnectionString
Using cmd As New OleDbCommand With {.Connection = cn}
cmd.CommandText =
<SQL>
SELECT * FROM
SELECT TOP 15 Identifier, ContactTitle, Country
FROM Customers
ORDER BY Identifier DESC
WHERE
ContactTitle ='Marketing Manager' AND Country = 'Germany'
</SQL>.Value
cn.Open()
Dim Reader = cmd.ExecuteReader
If Reader.HasRows Then
Return True
Else
Return False
End If
End Using
End Using
End Function
''' <summary>
''' This version we pass in values that the user supplied from TextBox controls
''' on a form.
''' </summary>
''' <returns></returns>
''' <remarks>
''' </remarks>
Public Function RealDemo(ByVal ContactTitle As String, ByVal Country As String) As Boolean
Using cn As New OleDbConnection With
.ConnectionString = Builder.ConnectionString
Using cmd As New OleDbCommand With {.Connection = cn}
cmd.CommandText =
<SQL>
SELECT * FROM
SELECT TOP 15 Identifier, ContactTitle, Country
FROM Customers
ORDER BY Identifier DESC
WHERE
ContactTitle = @ContactTitle AND Country = @Country
</SQL>.Value
Dim CompanyTitleParameter As New OleDbParameter With
.DbType = DbType.String,
.ParameterName = "ContactTitle",
.Value = ContactTitle
cmd.Parameters.Add(CompanyTitleParameter)
Dim CountryParameter As New OleDbParameter With
.DbType = DbType.String,
.ParameterName = "@Country",
.Value = Country
cmd.Parameters.Add(CountryParameter)
cn.Open()
Dim Reader = cmd.ExecuteReader
Dim Success As Boolean = Reader.HasRows
Reader.Close()
Return Success
End Using
End Using
End Function
End Module
Note the SQL is done slightly different than I gave before, I broke it down to first get our results, top 15 then used the result to do the where conditions.
IMPORTANT Some will tell you that MS-Access does not use named parameters as I have used, that is correct but it accepts them. Access uses ordinal position of how parameters were added. So why use named parameters? If you have a lot of parameters
it makes for easier time to figure out issues or errors in the code. Also if moving to SQL-Server this is the correct syntax, not ? marker. 
Please remember to mark the replies as answers if they help and unmark them if they provide no help, this will help others who are looking for solutions to the same or similar problem.