SQL query is not running IN VB.NET - sql

Question

I am fresher in VB.NET and I am trying to execute an SQL query in VB.NET but not showing any value at output. Can u please help me to find where am I going Wrong.
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim objConn As New SqlConnection(sConnectionString)
objConn.Open()
Dim sw ,readerObj
Dim sSQL As String = "select top 1 " & sw & " = e.import from tblrelcoms r , [beant].[dbo].tblequipments e where r.IDEquipment = e.IDEquipment"
Using readerObj As SqlClient.SqlDataReader = cmdObj.ExecuteReader
Dim objCmd As New SqlCommand(sSQL, objConn)
objCmd.ExecuteNonQuery()
TextBox1.Text = sw.ToString()

Answer 1

The problem you have is that you cannot just concatenate a variable into SQL and expect it to be updated once the SQL is executed.
ExecuteScalar is probably the easiest way of achieving what you want:
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
TextBox1.Text = command.ExecuteScalar().ToString()
End Using
End Using
Although if you need more than one column, then you could use a data reader:
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
Using reader = command.ExecuteReader()
If reader.Read()
TextBox1.Text = reader.GetString(0)
End If
End Using
End Using
End Using
I have made a couple of other changes too.
Added Using blocks to ensure IDisposable objects are disposed of properly.
Updated the sql join syntax from ANSI 89 implicit joins to ANSI 92 explicit joins, as the name suggests the syntax you are using is 24 years out of date. There are many reasons to start using the new syntax, which is nicely covered in this article: Bad habits to kick : using old-style JOINs
Added an ORDER BY clause to your sql. TOP 1 without order by will give you indeterminate results (unless you only have one record, in which case top 1 is redundant)
A more complex solution would be to use output parameters, which will work and seems more in line with what you were originally trying to achieve, but is overkill for this situation (in my opinion):
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 #Output = e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
Dim p As SqlParameter = command.Parameters.Add("#Output", SqlDbType.VarChar, 255)
p.Direction = ParameterDirection.InputOutput
command.ExecuteNonQuery();
TextBox1.Text = p.Value.ToString()
End Using
End Using
*Please excuse any syntax errors, I have not used VB.Net in years, and some c# quirks may be in the below, such as I can't remember if you just don't have to use parentheses for a parameterless method, or if you can't... Hopefully there is enough basic structure to get you started