SQL like with multiple textboxes - sql

Question

For my company I have to create a customer database, which I manage over a VB.NET application.
The application has a few textboxes and a button to "Search" for a customer. If I type in the name of a customer the SQL Select statement is working and populating my datagrid.
But I want to be able to type in the name of the customer AND the street where he lives in. What is the best solution for this? using cases? using a lot of If statements?
Here is my code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If True Then
Dim Conn As New MySqlConnection
Dim da As MySqlDataAdapter
Dim ds As New DataSet
Dim dt As New DataTable
Dim plz As String = plzTextBox.Text
Conn.ConnectionString = "server=localhost;uid=root;pwd=;database=wws; "
Dim sql As String = String.Empty
If vornameTextBox.Text <> String.Empty Then
sql = "vorname = " & vornameTextBox.Text.Trim
End If
If nachnameTextBox.Text <> String.Empty Then
AddCondition(sql, "nachname LIKE '%" & nachnameTextBox.Text.Trim & "%'")
End If
If emailTextBox.Text <> String.Empty Then
AddCondition(sql, "email LIKE '%" & emailTextBox.Text.Trim & "%'")
End If
If plzTextBox.Text <> String.Empty Then
AddCondition(sql, "plz LIKE '%" & plzTextBox.Text.Trim & "%'")
End If
If sql <> String.Empty Then
da = New MySqlDataAdapter("SELECT id,vorname,nachname,email,plz,strasse,nummer,stiege,stock,tuer FROM kunden WHERE " + sql, Conn)
da.Fill(dt)
DataGridView1.DataSource = dt
End If
Else
DataGridView1.ColumnCount = 1
DataGridView1.Rows.Add("1")
End If
End Sub
Thanks in advance!

Answer 1

You can avoid using lots of if statements if you really want, but all you're doing is shunting a load onto your SQL server instead of having it on the client.
The example here is one where you can use lots of if statements or ternary operators to determine how you build your SQL statement, putting a very light processing load on the client, or you can just insert the text value of each of your fields, followed by a percentage sign and surrounded by single quotes, thus making your SQL server evaluate the contents of those fields when it otherwise wouldn't if the field is blank.
It's possible query plan optimization would remove those superfluous field searches, and maybe it wouldn't. I'm typing this on my phone and so don't have anything available to test with.