如何在 Access SQL 中使用 BETWEEN 和 AND 来过滤日期范围？

Question

I am using an Access database that has table Visits with field VisitDate whose values are stored as a strings (eg 01/21/2020 ). I need to extract all records using VisitDate fields values between 1/20/2020 and 1/26/2020 . The best I can do, after working on this problem for that last five days is...

dim WHEREclause as string = " WHERE VisitDate BETWEEN " & ccc & " AND " & ddd

where ccc is "01/20/2020" and ddd is "01/26/2020" . This gives me the correct records for year 2020, but it also return records from the same time period in 2019. How do I fix this problem?

Answer 1

Combining the comments by @LarsTech and @jmcilhinney. Use parameters and Convert the string field to a real date.

Private Sub OPCode(ccc As String, ddd As String)
    Dim dt As New DataTable
    Using cn As New OleDbConnection("Your connection string"),
    cmd As New OleDbCommand("Select * From Visits WHERE CDate(VisitDate) BETWEEN @FirstDate AND @SecondDate;")
        cmd.Parameters.Add("FirstDate", OleDbType.Date).Value = CDate(ccc)
        cmd.Parameters.Add("SecondDate", OleDbType.Date).Value = CDate(ddd)
        dt.Load(cmd.ExecuteReader)
    End Using
    DataGridView1.DataSource = dt
End Sub

Please be aware that with Access, the names of the Parameters do not matter. It is the order that the parameters appear in the sql statement must match the order that the parameters are added to the Parameters collection. I use descriptive names for readability.

Answer 2

Do it with #

dim WHEREclause as string = " WHERE VisitDate BETWEEN #" & ccc & "# AND #" & ddd & "#"

nb: beware of concatenating string, it facilitates sql injections