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我有一个 vb.net/SQL Server 客户端应用程序，我需要在其中向现有查询添加左连接。asp.net 使用数据层中的相同代码来检索应用程序的 Web 版本的数据。接下来的两个代码块显示了整个原始语句和带有所有连接的新语句。我建议您跳到较低的代码块，这些代码块要小得多来说明问题。原始查询：

    select q.qasr_id as Id,
           q.qasr_identification_number as IdentificationNumber,
           q.status as Status,
           b.business_unit_name as BusinessUnitName,
           b.business_unit_id as BusinessUnitId,
           u.login as Originator,
           q.date_created as DateCreated,
           q.po_number as PoNumber,
           q.po_part_number as PoPartNumber,
           q.po_part_rev as PoPartRev,
           q.lot_quantity as LotQuantity,
           q.control_number as ControlNumber,
           q.item_number as PoItem,
           q.buyer as Buyer,
           q.buyercode as BuyerCode,
           q.spe as Spe,
           p.program as ProgramName,
           l.product_line as productline,
           s.ent_supplier_nbr as SupplierEsd,
           s.sup_name1 as SupplierName,
           c.commodity_code as CommodityCode,
           a.agency_name as AgencyName,
           q.verifyid as AgencyDocId,
           q.activity as Activity,
           case q.isdeleted when 1 then 'Deleted' else '' end as Deleted
      from qasr q
      join auth_user u on q.auth_user_id = u.auth_user_id
      join functional_area f on q.functional_area_id = f.functional_area_id
      join business_unit b on f.business_unit_id = b.business_unit_id
      left join suppliers s on q.supplier_id = s.supplier_id
      left join programs p on q.program_id = p.program_id
      left join product_lines l on p.product_line_id = l.product_line_id
      left join commodities c on q.commodity_id = c.commodity_id
      left join agency a on q.agency_id = a.agency_id
       where b.business_unit_id = @BusinessUnitId
         and q.isdeleted = @IsDeleted

新查询：

    select q.qasr_id as Id,
           q.qasr_identification_number as IdentificationNumber,
           q.status as Status,
           b.business_unit_name as BusinessUnitName,
           b.business_unit_id as BusinessUnitId,
           u.login as Originator,
           q.date_created as DateCreated,
           q.po_number as PoNumber,
           q.po_part_number as PoPartNumber,
           q.po_part_rev as PoPartRev,
           q.lot_quantity as LotQuantity,
           q.control_number as ControlNumber,
           q.item_number as PoItem,
           q.buyer as Buyer,
           q.buyercode as BuyerCode,
           q.spe as Spe,
           p.program as ProgramName,
           l.product_line as productline,
           s.ent_supplier_nbr as SupplierEsd,
           s.sup_name1 as SupplierName,
           c.commodity_code as CommodityCode,
           a.agency_name as AgencyName,
           q.verifyid as AgencyDocId,
           q.activity as Activity,
           case q.isdeleted when 1 then 'Deleted' else '' end as Deleted,
           case when m.d_count > 0 then 'Yes' else 'No' end as Dispositioned
      from qasr q
      join auth_user u on q.auth_user_id = u.auth_user_id
      join functional_area f on q.functional_area_id = f.functional_area_id
      join business_unit b on f.business_unit_id = b.business_unit_id
      left join suppliers s on q.supplier_id = s.supplier_id
      left join programs p on q.program_id = p.program_id
      left join product_lines l on p.product_line_id = l.product_line_id
      left join commodities c on q.commodity_id = c.commodity_id
      left join agency a on q.agency_id = a.agency_id
      left join (select qasr_id as qasr_id, count(1) as d_count
                   from qasr_metric
                  where d = 1
                  group by qasr_id) m on m.qasr_id = q.qasr_id
       where b.business_unit_id = @BusinessUnitId
         and q.isdeleted = @IsDeleted

新查询将左连接添加到第二个表 (qasr_metric)，以确定第二个表是否包含任何关联行，列“D”中的值为 1。qasr_metric 表由 (quasr_id, d) 索引，这就是性能受到最小影响的原因。删除所有其他列和连接归结为：

    select q.qasr_id as Id from qasr q

和

    select q.qasr_id as Id,
           case when m.d_count > 0 then 'Yes' else 'No' end as Dispositioned
      from qasr q
      left join (select qasr_id as qasr_id, count(1) as d_count
                   from qasr_metric
                  where d = 1
                  group by qasr_id) m on m.qasr_id = q.qasr_id

应用程序的 asp.net 端的新查询的性能在原始查询的大约 3 秒内，如果我在 SQL Server Mgmt Studio 中单独运行查询，情况也是如此。但是，应用程序的客户端在几秒钟内处理原始查询的结果，而新查询则需要一个多小时，这是荒谬的。查看 vb 代码本身，数据层使用参数化查询调用 ExecuteReader，对于原始查询和新查询几乎立即完成。问题出现在业务层中，该业务层使用 dr 作为由 ExecuteReader 填充的读取器调用。每行返回的数据用于填充新对象 (InspectionDocumentSummary)，这些对象的列表用于填充显示给用户的 DataGridView。

    Private Sub Fetch(ByVal dr As SafeDataReader)
       Using dr
          While dr.Read()
             Add(InspectionDocumentSummary.GetInspectionDocumentSummary(dr))
             _id = dr.GetGuid("Id")
             _identificationNumber = dr.GetString("IdentificationNumber")
             _status = dr.GetString("Status")
             _originator = dr.GetString("Originator")
             _dateCreated = dr.GetSmartDate("DateCreated")
             _poPartNumber = dr.GetString("PoPartNumber")
             _poPartRev = dr.GetString("PoPartRev")
             _lotQuantity = Convert.ToString(dr.GetInt32("LotQuantity"))
             _buyer = dr.GetString("Buyer")
             _spe = dr.GetString("Spe")
             _agencyDocId = dr.GetString("AgencyDocId")
             _agencyName = dr.GetString("AgencyName")
             _activity = dr.GetString("Activity")
             _controlNumber = dr.GetString("ControlNumber")
             _dispositioned = dr.GetString("Dispositioned")
             _programName = dr.GetString("ProgramName")
             _supplierEsd = dr.GetString("SupplierEsd")
             _supplierName = dr.GetString("SupplierName")
             _commodityCode = dr.GetString("CommodityCode")
          End While
       End Using
    End Sub

对于原始查询，这几乎立即完成，但新查询需要一个多小时。我的理解是 ExecuteReader 检索数据，而 dr.Read 循环只是将返回的数据读入正在填充的 DataGridView（在我的情况下没有其他数据处理）。我将上面代码中的“_dispositioned = dr.GetString("Dispositioned")" 替换为 "_dispositioned = "Yes"" 没有任何变化，因此读取的数据本身不是问题。有什么建议么？

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1 回答 1

0

像这样的许多问题都发生在查询中被转换为字符串的类型上，例如当比较或连接一侧的 varchar 和另一侧的 int 时。

如果直接从数据库运行查询而没有性能问题，请尝试运行查询，并在数据读取器读取如下行后让 .NET 进行数据类型转换：

Private Sub Fetch(ByVal dr As SafeDataReader)
   Using dr
      While dr.Read()
         Add(InspectionDocumentSummary.GetInspectionDocumentSummary(dr))
         _id = GUID.Parse(dr("Id"))
         _identificationNumber = dr("IdentificationNumber")
         _status = dr("Status")
         _originator = dr("Originator")
         _dateCreated = dr.GetSmartDate("DateCreated")
         _poPartNumber = dr("PoPartNumber")
         _poPartRev = dr("PoPartRev")
         _lotQuantity = Convert.ToString(dr.GetInt32("LotQuantity"))
         _buyer = dr("Buyer")
         _spe = dr("Spe")
         _agencyDocId = dr("AgencyDocId")
         _agencyName = dr("AgencyName")
         _activity = dr("Activity")
         _controlNumber = dr("ControlNumber")
         _dispositioned = dr("Dispositioned")
         _programName = dr("ProgramName")
         _supplierEsd = dr("SupplierEsd")
         _supplierName = dr("SupplierName")
         _commodityCode = dr("CommodityCode")
      End While
   End Using
End Sub

如果这无济于事，请尝试在不调用的情况下运行它，Add以确保该方法中的某些内容不会导致问题。

于 2017-07-19T23:14:35.257 回答