vb.net trim word from end of string - sql

Question

I am trying to run an SQL query in my vb.net application using a loop
SQL = "SELECT * FROM table WHERE "
For m = 1 To num_array
SQL = SQL & "type = '" & array(m, 1) & "' OR "
Next
but its showing an OR at the end.
how can i trim this last OR from my query?

Answer 1

This seems a job for a StringBuilder
Dim sql = new StringBuilder("SELECT * FROM table WHERE ")
For m = 1 To num_array
sql.Append("type = '" & array(m, 1) & "' OR ")
Next
If num_array > 0 Then
sql.Length -= 4
End If
However you should pay special care to your string concatenation. It seems that your array doesn't contain numbers but string because you are putting everything between single quotes and this means that your type field is a string not a number.
Of course I hope that your array content is not directly inserted by your user otherwise you have a big security risk called Sql Injection. Anyway look at how to build a parameterized query.
Something like this
Dim prms = New List(Of SqlParameter)()
Dim num_Array = 4
Dim sql = New StringBuilder("SELECT * FROM table WHERE ")
For m = 1 To num_array
sql.Append("type = #p" & m & " OR ")
prms.Add(New SqlParameter("#p" & m, array(m, 1)))
Next
If num_array > 0 Then
sql.Length -= 4
End If
Dim cmd = new SqlCommand(sql.ToString(), connection)
cmd.Parameters.AddRange(prms.ToArray())