How do I get dataset from the query? - sql

Question

I have the following SQL query in MS Access / VB.net:
Dim sql = "SELECT [Product Name], [Customer Name], [Group Associated], [Customer Address], [Product Price], [Current Stock], [Date Ordered], [Volume Purchased] FROM (torder INNER JOIN tproducts ON tproducts.Product_ID = torder.Product_ID) INNER JOIN tcustomer ON torder.Customer_ID = tcustomer.Customer_ID WHERE torder.[Date Ordered] Between #" & StartOfTimePeriod & "# And #" & Today & "#;"
conn.Open()
Dim dataAdapter As New OleDbDataAdapter(sql, conn)
Dim ds As New DataSet()
dataAdapter.Fill(ds, "torder")
conn.Close()
DataGridView.DataSource = ds
DataGridView.DataMember = "torder"
When the query is run it doesn't display the full dataset that it should. Instead, the results are almost random. What could be wrong?
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Answer 1

Do not stringize your date and time values. Use a parameterized query.
Dim sql = "SELECT [Product Name], [Customer Name], [Group Associated], " & _
"[Customer Address], [Product Price], [Current Stock], [Date Ordered], " & _
"[Volume Purchased] " & _
"FROM (torder INNER JOIN tproducts ON tproducts.Product_ID = torder.Product_ID) " & _
"INNER JOIN tcustomer ON torder.Customer_ID = tcustomer.Customer_ID " & _
"WHERE torder.[Date Ordered] >= ? And torder.[Date Ordered] <= ?"
Dim dataAdapter As New OleDbDataAdapter(sql, conn)
Dim p1 = new OleDbParameter() With
{
.ParameterName = "#p1",
.OleDbType = OleDbType.Date,
.Value = StartOfTimePeriod
}
Dim p1 = new OleDbParameter() With
{
.ParameterName = "#p2",
.OleDbType = OleDbType.Date,
.Value = DateTime.Today.AddMinutes(1339)
}
dataAdapter.SelectCommand.Parameters.Add(p1)
dataAdapter.SelectCommand.Parameters.Add(p2)
....
In this way the correct interpretation of your DateTime values is a job passed to the database engine together with actual DateTime values (I assume that StartOfTimePeriod is a DateTime variable).
Instead, if you convert these values to string, the conversion follow the rules of your locale environment that could produce a string not compatible with the expected format of your database engine (for example the inversion of position of months and days values)