Select max visual studio 2010

Question

I'm updating a program from Visual Basic 6 to Visual Studio 2010 and, of course, I have founded a lot of problems so solve.

I'm using Access database with four tables with the same Key (Indice).

If I use the code as follow, I can get the last record from CodDekafix Table:

Private Sub cmdLast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles   cmdLast.Click
    Dim Con As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\DEKAFIX\Consulta Dekafix\dekafix.mdb")
    Dim cmd As New OleDbCommand()
    Con.Open()
    sql = "Select * From Indice Where CodDekafix=(Select max(CodDekafix) From Indice)"

But If I want to get all the results from all tables with the same Key (Indice) with the change as showed below the program doesn't work.

sql = "Select * from Indice, dekafix1, dekafix2, dekafix3" _
      & " where CodDekafix=(Select max(CodDekafix) From Indice) and" _
      & " Indice.CodDekafix = dekafix1.CodDekafix and" _
      & " dekafix1.CodDekafix=dekafix2.CodDekafix and" _
      & " dekafix2.CodDekafix=dekafix3.CodDekafix and" _
      & " ORDER BY Indice.CodDekafix"

Answer 1

Your SQL code in the second code sample is invalid. When we strip out the formatting representing the string in VB code, you get this:

Select * from Indice, dekafix1, dekafix2, dekafix3
where CodDekafix=(Select max(CodDekafix) From Indice) and
Indice.CodDekafix = dekafix1.CodDekafix and
dekafix1.CodDekafix=dekafix2.CodDekafix and
dekafix2.CodDekafix=dekafix3.CodDekafix and
ORDER BY Indice.CodDekafix

You have two problems here:

1) There's an extra "and" before the ORDER BY clause. Remove it.

2) The first line of your WHERE clause has an ambiguous reference to CodDekafix -- you need to specify what table that's coming from. Replacing CodDekafix with Indice.CodDekafix should do the trick.

sql = "Select * from Indice, dekafix1, dekafix2, dekafix3" _
  & " where Indice.CodDekafix=(Select max(CodDekafix) From Indice) and" _
  & " Indice.CodDekafix = dekafix1.CodDekafix and" _
  & " dekafix1.CodDekafix=dekafix2.CodDekafix and" _
  & " dekafix2.CodDekafix=dekafix3.CodDekafix" _
  & " ORDER BY Indice.CodDekafix"