Dim cmd1 As New SQLCommand
cmd1.C '记得设置数据源名称
cmd1.CommandText = "S elect * From 订单 where 编码 = '614-1' "
Dim dt1 As DataTable = cmd1.ExecuteReader
Dim cmd5 As New SQLCommand
cmd5.C '记得设置数据源名称
For Each dr1 As DataRow In dt1.DataRows
cmd5.CommandText = "S elect * From 表a where 编码 = '"& dr1("编码") &"'"
Dim dt5 As DataTable = cmd5.ExecuteReader
Dim val As Double = dt5.Compute("sum(用量)", "编码= '"& dr1("编码") &"'")
dr1("余量") = dr1("数量") - val
Next
这里如何生产一个临时表，余量> 0 的。另外，这种遍历，如何提高下效率。数据多时，速度慢。
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Post By：2020/4/2 15:08:00 [只看该作者]
