以下是销售订单表、产品工序单价主表来自一个数据源

Dim cmd As New SQLCommand
Dim dt As DataTable
cmd.C
cmd.CommandText = "Select * FROM {销售订单表} where 生产任务单号 not in (Select 生产任务单号 FROM {产品工序单价主表}) "
dt = cmd.ExecuteReader()

如果销售订单表、产品工序单价主表分别来自不同的数据源 ERP、GZXT

请问不同数据源如何编写以下代码？

Select语句中的表，必须是同一个数据源，铁律。

有思路，但是数据量很大的时候，效率会比较低：
 
cmd1.CommandText = "Select Distinct 生产任务单号 FROM {产品工序单价主表}"

dim s as string
dt = cmd1.ExcuteReader()
for each dr as datarow in dr.datarows

   if s > "" then

      s = s & ","

   end if

    s= s & dr("生产任务单号 ")

next

cmd2.commandtext = "Select * FROM {销售订单表} where 生产任务单号 not in (" & s & ")"

cmd1.CommandText = "Select Distinct 生产任务单号 FROM {产品工序单价主表}"

dim s as string
dt = cmd1.ExcuteReader()
for each dr as datarow in dr.datarows

   if s > "" then

      s = s & ","

   end if

    s= s & dr("生产任务单号 ")

next

cmd2.commandtext = "Select * FROM {销售订单表} where 生产任务单号 not in (" & s & ")"

这段代码是错的，执行不了

这个代码是给你示意的，给的是一个思路，具体自己调试分析。

Dim cmd1 As New SQLCommand
Dim cmd2 As New SQLCommand
Dim s As String
Dim dt As DataTable
cmd1.Connection Name = "数据源1"
cmd2.Connection Name = "数据源2"
cmd1.CommandText = "Select Distinct 生产任务单号 FROM {产品工序单价主表}"
dt = cmd1.ExecuteReader
For Each dr As DataRow In dt.datarows
   If s > "" Then
      s = s & ","
   End If
    s = s & "\'" & dr("生产任务单号 ") & "\'"
Next
cmd2.commandtext = "Select * FROM {销售订单表} where 生产任务单号 not in (" & s & ")"
dt = cmd2.ExecuteReader