Question

我在MS Access / VB.net中有以下SQL查询：

    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"

运行查询时，它不会显示应该完整的数据集。相反，结果几乎是随机的。可能有什么不对？

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Answer 1

请勿对日期和时间值进行字符串化。使用参数化查询。

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)
....

通过这种方式，对DateTime值的正确解释是与实际DateTime值一起传递给数据库引擎的作业（我假设StartOfTimePeriod是DateTime变量）。相反，如果将这些值转换为字符串，则转换将遵循您的语言环境的规则，这些规则可能会生成与数据库引擎的预期格式不兼容的字符串（例如，月份和日期值的位置反转）

如何从查询中获取数据集？

1 个答案: