修改:tsql1 = "select sum(产品单价) from 订单估算成本 where 车型 = Combo1.Text and 翻转机构 = Combo2.Text and 箱体材质 = Combo3.Text"
为:
tsql1 = "select sum(产品单价) from 订单估算成本 where 车型='" & Combo1.Text & "' and 翻转机构='" & Combo2.Text & "' and 箱体材质='" & Combo3.Text & "'"
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