主题：关于SQL计算问题

请看下面代码？

Dim dt1 As Date = #1/1/2016#
Dim dt2 As Date = #12/31/2016#
Dim wbe As Double

Dim cmd As New S QLCo mmand
Dim dt As DataTable
cmd.C
cmd.Com mandText = "S ELEC T [产品数量] * [外币] As [外币金额] Fro m {订单明细表} where _Identify is null "
dt = cmd.ExecuteReader()

wbe =Round2(dt.SQLCompute("Sum(外币金额)","订单编号 in (Select [_Identify] fro m {订单主表} where 订单日期 >= '' and 订单日期 <= '' and SID = 1)"),2)