更改DateTime值的格式

Question

每个人似乎都讨厌DateTime价值观.

在我的项目中,我有一个SQL SELECT查询来查找匹配参数值的数据库中的结果.

我的代码是:

Dim where As String = "WHERE [Supp_Code] = @scode " & _
    "AND [DateFrom] = @datfrom " & _
    "AND [DateTo] = @datto " & _
    "AND [Comm_Code] = @ccode " & _
    "AND [Customer_Code] = @custcode "

Dim sql As String = "SELECT [Comm_Code], [AqYear] FROM [Acquisition Commission] "

sql &= where & " ORDER BY [AqYear] ASC"

Dim cmd As New OleDb.OleDbCommand(sql, con)
cmd.Parameters.AddWithValue("@scode", cmbSupp.Text.Trim)
cmd.Parameters.AddWithValue("@datfrom", datFrom.Value)
cmd.Parameters.AddWithValue("@datto", datTo.Value)
cmd.Parameters.AddWithValue("@ccode", txtCommCode.Text)
cmd.Parameters.AddWithValue("@custcode", cmbCustomerCode.Text)

Dim daYear As New OleDb.OleDbDataAdapter(cmd)
Dim dsYear As New DataSet
daYear.Fill(dsYear)

代码本身没有问题.问题是DataSet只有0行,因为(它是一个控件)的DateTime格式是'MM/dd/yyyy',但在数据库中它存储为'dd/MM/yyyy'.datFrom.ValueDateTimePicker

在将其用作参数之前,将正确的数据库格式转换为最简单的方法是什么？

编辑

使用下面的评论/答案,我已将我的代码改编为以下内容:

 Dim test As DateTime
 Dim test2 As DateTime
    test = ugDates.ActiveRow.Cells("DateFrom").Value
    test = ugDates.ActiveRow.Cells("DateTo").Value

 Try
  Dim where As String = "WHERE [Supp_Code] = @scode " & _
       "AND [DateFrom] = @datfrom " & _
       "AND [DateTo] = @datto " & _
       "AND [Comm_Code] = @ccode " & _
       "AND [Customer_Code] = @custcode "

Dim sql As String = "SELECT DISTINCT [Comm_Code], [AqYear] FROM [Acquisition Commission] "

    sql &= where & " ORDER BY [AqYear] ASC"

    Dim cmd As New OleDb.OleDbCommand(sql, con)
     cmd.Parameters.Add("@scode", OleDbType.VarChar).Value = cmbSupp.Text
     cmd.Parameters.Add(New OleDbParameter("@datfrom", OleDbType.Date).Value = test)
     cmd.Parameters.Add(New OleDbParameter("@datto", OleDbType.Date).Value = test2)
     cmd.Parameters.Add("@ccode", OleDbType.VarChar).Value = txtCommCode.Text
     cmd.Parameters.Add("@custcode", OleDbType.VarChar).Value = cmbCustomerCode.Text

但是,它在第​​二个参数上给出了以下错误:

OleDbParameterCollection仅接受非null的OleDbParameter类型对象,而不接受布尔对象.

Answer 1

问题是DataSet只有0行,因为datFrom.Value(它是一个DateTimePicker控件)的DateTime格式是'MM/dd/yyyy',但在数据库中它存储为'dd/MM/yyyy ".

除非您将日期存储为字符串,否则这可能不是问题.日期是结构,而不是字符串,并且本质上没有格式.格式化是应用于字符串的内容.它类似于一个像int或decimal的数字.如果此字段确实是字符串,则应重新访问模式并相应地更新类型.

您很可能尝试将参数值或查询值中的日期与时间进行比较.

• 使用DateValue函数调整存储数据库的时间
• 使用.Date日期值仅比较值日期

码:

Dim where As String = "WHERE [Supp_Code] = @scode " & _
        "AND DateValue([DateFrom]) = @datfrom " & _ 
        "AND DateValue([DateTo]) = @datto " & _
        "AND [Comm_Code] = @ccode " & _
        "AND [Customer_Code] = @custcode "


// select either OleDbType.Date or OleDbType.DBDate

cmd.Parameters.Add(new OleDbParameter("@datfrom", OleDbType.Date) With {.Value = datFrom.Value.Date})
cmd.Parameters.Add(new OleDbParameter("@datto", OleDbType.Date) With {.Value = datTo.Value.Date})

另一个可能的问题是逻辑,为什么不这样做之间或范围检查,而不是在相等性检查DateFrom和DateTo？

"AND DateValue([DateFrom]) >= @datfrom " & _ 
"AND DateValue([DateTo]) <= @datto " & _

理想情况下,你会在这里使用相同的值两个@datfrom和@datto.上面的查询将是具有跨越传入日期参数​​的开始/结束日期的任何项目.