how to inner join two tables or more tables from ms access database with vb.net? - vb.net

Question

I have three tables in access database and a Application in vb.net where i am trying to search data from all three tables by TextBox but it is giving error.can someone tell me how to do this?
enter code here
Private Sub check()
Dim Myconn As New OleDbConnection(constr)
Dim adapter As New OleDbDataAdapter()
Dim command As New OleDbCommand()
Dim sql = "select descriptionofgoods,remarks,mode from tabel1 INNER JOIN table2 ON tabel1.id = tabel2.id inner join tabel3 on tabel1.id = tabel3.id;"
Try
Myconn.Open()
dt.Clear()
If TextBox2.Text > "" Then
sql = sql & " and [id] = ? "
command.Parameters.AddWithValue("id", TextBox1.Text)
End If
command.Connection = Myconn
command.CommandText = sql
adapter.SelectCommand = command
adapter.Fill(dt)
If dt.Rows.Count > 0 Then
DataGridView1.DataSource = dt
DataGridView1.Refresh()
Else
MessageBox.Show("ITEM NOT FOUND")
End If
Catch exp As Exception
Throw exp
Finally
If Myconn IsNot Nothing Then Myconn.Close()
End Try
End Sub

Answer 1

A lot of your code is redundant and can be removed:
Using da as New OleDbDataAdapter("select descriptionofgoods,remarks,mode from tabel1 INNER JOIN table2 ON tabel1.id = tabel2.id inner join tabel3 on tabel1.id = tabel3.id", constr)
Dim dt = DirectCast(DataGridView1.DataSource, DataTable)
dt.BeginLoadData()
dt.Clear()
If Not string.IsNullOrEmpty(TextBox2.Text) Then
da.SelectCommand.CommandText &= " and tabel1.[id] = ? "
da.SelectCommand.Parameters.AddWithValue("id", TextBox1.Text) 'why is this TextBox1 when you tested textbox2 in the If?
End If
adapter.Fill(dt)
dt.EndLoadData()
End Using
Notes:
Use Using; you then don't need your Try/Finally
DataAdapter knows how to create and open a connection itself
Don't catch exceptions only to throw them again; it disrupts the stack trace. Dont put a catch at all if youre not going to catch anything; Try ... Finally is legal, Throw on its own is legal (doesn't disrupt stack trace)
Do not terminate an SQL with a semicolon if you want to add to it. Don't terminate a single statement SQL with a semicolon anyway
You have several tables with an ID column; Access might let you get away with not specifying which ID you're talking about but proper databases won't so get in the habit now of fully qualifying every column (in your select too)
See the comment about TextBox1/TextBox2
Please.. name your controls properly. "name of a type of object plus a serial number" is not a good name for anything; your name is Pankaj Babbar, not human105874274365. You name your local variables well but not your class level ones, which is definitely the wrong way round
To rename a control after you add it to a windows form, click on it, then change then text in the (Name) line of the property grid
Telling a datatable youre about to/have finished loading data improves performance
Bound controls update automatically (if you ever use BindingSource investigate the RaiseListChangedEvents setting too)