Question

我在同一服务器的同一数据库中制作了具有相同索引的表的副本。然后它在一个表和另一个表中执行相同的查询，但执行计划是不同的。

为什么？

这些是我的疑问：

select top 1 * from SFMatl
where AppUpdated = 0 and UpdLock = 0 and CompanyId = 'ent'
order by recid

select top 1 * from SFMatl_Backup20042017
where AppUpdated = 0 and UpdLock = 0 and CompanyId = 'ent'
order by recid

这些执行计划：

Query1

Query2

我的创建表：

/****** Object:  Table [dbo].[SFMatl_Backup20042017]    Script Date: 20/04/2017 14:40:33 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[SFMatl_Backup20042017](
    [RecId] [int] NOT NULL,
    [CompanyId] [char](3) NOT NULL,
    [PrOdId] [varchar](10) NOT NULL,
    [OprNum] [tinyint] NOT NULL,
    [WrkCtrId] [varchar](10) NOT NULL,
    [ItemId] [varchar](20) NOT NULL,
    [SizeId] [varchar](20) NOT NULL,
    [SizeId2] [varchar](20) NOT NULL,
    [ColorId] [varchar](20) NOT NULL,
    [MatlPropId] [varchar](8) NOT NULL,
    [LineNum] [tinyint] NOT NULL,
    [SubForLineNum] [tinyint] NOT NULL,
    [SerialNum] [varchar](20) NOT NULL,
    [PalletNum] [varchar](20) NOT NULL,
    [BatchNum] [varchar](20) NOT NULL,
    [PQty] [numeric](28, 12) NOT NULL,
    [PUnit] [varchar](10) NOT NULL,
    [SQty] [numeric](28, 12) NOT NULL,
    [SUnit] [varchar](10) NOT NULL,
    [TQty] [numeric](28, 12) NOT NULL,
    [TUnit] [varchar](10) NOT NULL,
    [StkQty] [numeric](28, 12) NOT NULL,
    [StkUnit] [varchar](10) NOT NULL,
    [FtQty] [numeric](28, 12) NOT NULL,
    [LbQty] [numeric](28, 12) NOT NULL,
    [MQty] [numeric](28, 12) NOT NULL,
    [KgQty] [numeric](28, 12) NOT NULL,
    [Yield] [numeric](28, 12) NOT NULL,
    [YieldUnit] [varchar](10) NOT NULL,
    [WPQty] [numeric](28, 12) NOT NULL,
    [WPUnit] [varchar](10) NOT NULL,
    [WSQty] [numeric](28, 12) NOT NULL,
    [WSUnit] [varchar](10) NOT NULL,
    [SetNum] [int] NOT NULL,
    [LaneNum] [tinyint] NOT NULL,
    [RowNum] [smallint] NOT NULL,
    [TranType] [varchar](10) NOT NULL,
    [WasteId] [varchar](10) NOT NULL,
    [Shift] [varchar](10) NOT NULL,
    [ShiftTime] [datetime] NOT NULL,
    [ShiftDate] [datetime] NOT NULL,
    [PRGCode] [varchar](10) NOT NULL,
    [UserRemark] [text] NOT NULL,
    [JobType] [varchar](10) NOT NULL,
    [WareHouseId] [varchar](10) NOT NULL,
    [LocationId] [varchar](10) NOT NULL,
    [AppUpdated] [tinyint] NOT NULL,
    [OnOffUpdated] [tinyint] NOT NULL,
    [InventTransId] [varchar](20) NOT NULL,
    [OrgSerialNum] [varchar](100) NOT NULL,
    [ReworkFlag] [tinyint] NOT NULL,
    [Reworked] [tinyint] NOT NULL,
    [Category] [varchar](50) NOT NULL,
    [GroupTranNum] [varchar](10) NOT NULL,
    [SystemCreated] [tinyint] NOT NULL,
    [OfflineTran] [tinyint] NOT NULL,
    [UpdLock] [tinyint] NOT NULL,
    [UpdLockTime] [datetime] NOT NULL,
    [SFBOMRevision] [int] NOT NULL,
    [UDF01] [varchar](50) NOT NULL,
    [UDF02] [varchar](50) NOT NULL,
    [AddEdit] [tinyint] NOT NULL,
    [CalcGauge] [numeric](28, 12) NOT NULL,
    [MasterSerial] [varchar](100) NOT NULL,
    [OprSerialCount] [smallint] NOT NULL,
    [QACheck] [tinyint] NOT NULL,
    [SpliceCount] [tinyint] NOT NULL,
    [NumAcross] [tinyint] NOT NULL,
    [PermitNum] [int] NOT NULL,
    [TransAs] [char](1) NOT NULL,
    [CreateTime] [datetime] NOT NULL,
    [ModifyTime] [datetime] NOT NULL,
    [OSUser] [varchar](20) NOT NULL,
    [ComputerName] [varchar](40) NOT NULL,
    [Reassign] [tinyint] NOT NULL,
    [Reassigned] [tinyint] NOT NULL,
    [OprCode] [varchar](10) NOT NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

/****** Object:  Table [dbo].[SFMatl]    Script Date: 20/04/2017 14:40:03 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[SFMatl](
    [RecId] [int] IDENTITY(1,1) NOT NULL,
    [CompanyId] [char](3) NOT NULL,
    [PrOdId] [varchar](10) NOT NULL,
    [OprNum] [tinyint] NOT NULL,
    [WrkCtrId] [varchar](10) NOT NULL,
    [ItemId] [varchar](20) NOT NULL,
    [SizeId] [varchar](20) NOT NULL,
    [SizeId2] [varchar](20) NOT NULL,
    [ColorId] [varchar](20) NOT NULL,
    [MatlPropId] [varchar](8) NOT NULL,
    [LineNum] [tinyint] NOT NULL,
    [SubForLineNum] [tinyint] NOT NULL,
    [SerialNum] [varchar](20) NOT NULL,
    [PalletNum] [varchar](20) NOT NULL,
    [BatchNum] [varchar](20) NOT NULL,
    [PQty] [numeric](28, 12) NOT NULL,
    [PUnit] [varchar](10) NOT NULL,
    [SQty] [numeric](28, 12) NOT NULL,
    [SUnit] [varchar](10) NOT NULL,
    [TQty] [numeric](28, 12) NOT NULL,
    [TUnit] [varchar](10) NOT NULL,
    [StkQty] [numeric](28, 12) NOT NULL,
    [StkUnit] [varchar](10) NOT NULL,
    [FtQty] [numeric](28, 12) NOT NULL,
    [LbQty] [numeric](28, 12) NOT NULL,
    [MQty] [numeric](28, 12) NOT NULL,
    [KgQty] [numeric](28, 12) NOT NULL,
    [Yield] [numeric](28, 12) NOT NULL,
    [YieldUnit] [varchar](10) NOT NULL,
    [WPQty] [numeric](28, 12) NOT NULL,
    [WPUnit] [varchar](10) NOT NULL,
    [WSQty] [numeric](28, 12) NOT NULL,
    [WSUnit] [varchar](10) NOT NULL,
    [SetNum] [int] NOT NULL,
    [LaneNum] [tinyint] NOT NULL,
    [RowNum] [smallint] NOT NULL,
    [TranType] [varchar](10) NOT NULL,
    [WasteId] [varchar](10) NOT NULL,
    [Shift] [varchar](10) NOT NULL,
    [ShiftTime] [datetime] NOT NULL,
    [ShiftDate] [datetime] NOT NULL,
    [PRGCode] [varchar](10) NOT NULL,
    [UserRemark] [text] NOT NULL,
    [JobType] [varchar](10) NOT NULL,
    [WareHouseId] [varchar](10) NOT NULL,
    [LocationId] [varchar](10) NOT NULL,
    [AppUpdated] [tinyint] NOT NULL,
    [OnOffUpdated] [tinyint] NOT NULL,
    [InventTransId] [varchar](20) NOT NULL,
    [OrgSerialNum] [varchar](100) NOT NULL,
    [ReworkFlag] [tinyint] NOT NULL,
    [Reworked] [tinyint] NOT NULL,
    [Category] [varchar](50) NOT NULL,
    [GroupTranNum] [varchar](10) NOT NULL,
    [SystemCreated] [tinyint] NOT NULL,
    [OfflineTran] [tinyint] NOT NULL,
    [UpdLock] [tinyint] NOT NULL,
    [UpdLockTime] [datetime] NOT NULL,
    [SFBOMRevision] [int] NOT NULL,
    [UDF01] [varchar](50) NOT NULL,
    [UDF02] [varchar](50) NOT NULL,
    [AddEdit] [tinyint] NOT NULL,
    [CalcGauge] [numeric](28, 12) NOT NULL,
    [MasterSerial] [varchar](100) NOT NULL,
    [OprSerialCount] [smallint] NOT NULL,
    [QACheck] [tinyint] NOT NULL,
    [SpliceCount] [tinyint] NOT NULL,
    [NumAcross] [tinyint] NOT NULL,
    [PermitNum] [int] NOT NULL,
    [TransAs] [char](1) NOT NULL,
    [CreateTime] [datetime] NOT NULL,
    [ModifyTime] [datetime] NOT NULL,
    [OSUser] [varchar](20) NOT NULL,
    [ComputerName] [varchar](40) NOT NULL,
    [Reassign] [tinyint] NOT NULL,
    [Reassigned] [tinyint] NOT NULL,
    [OprCode] [varchar](10) NOT NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

Answer 1

与这些查询的主要区别在于它们不相同 SELECTed表不一样。

这意味着在查询计划方面有两件事例如，由于数据量不同，统计数据不同不同的索引或索引碎片
您可以检查索引及其碎片（如果需要，可以重建/重新组织它们），您也可以重新计算统计数据。

如果仍然保持相同的查询计划，则那么差异主要是由于表中包含的数据。

Answer 2

主要参数之一，sql server在创建计划时使用的是统计数据。所以即使两个表中的数据相同，统计数据也会不同，这会导致执行计划不同

要查看表格的统计信息，您可以使用以下

 dbcc show_statistics('SFMatl','AppUpdated')


 dbcc show_statistics('SFMatl','SFMatl_Backup20042017')

如果您现在，如何推断上述结果，您将能够看到，上述两个表的统计数据不同，这进一步决定了计划质量

相同的查询但不同的执行计划，同一服务器

2 个答案: