主题：[求助]有关SQL查询表问题

Dim TbNm,sql As String

TbNm = "查询"

If MainTable.Name = Tbnm  Then

    sql  = "Select a.*,iif(有效期至 < Date() , Null, 有效期至) As 有效期至, iif(有效期至 < Date() , Null, 证书编号) As 证书编号 From{设备清单} a "

    sql+="Left JOIN (Select 仪器编号,Max(证书编号) As 证书编号,Max(有效期至) As 有效期至 From{检定数据} group by 仪器编号) b ON a.仪器编号 = b.仪器编号"

    DataTables(TbNm).Fill(sql,"",True)

End If