通過程序獲得SQL Server自增型字段的函數:GetKey

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概述:

通過程序來產生自增型字段,可以避免多用戶操作的讀取臟數據,操作也很簡便.可以更好的在程序中控制這些關鍵字段的數值.

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關鍵步驟:

1.???? 創建用于存放需要自增的數據表.(systemkey)

SQL Script 如下:

if?exists?(select?*?from?dbo.sysobjects?where?id?=?object_id(N'[dbo].[SystemKey]')?and?OBJECTPROPERTY(id,?N'IsUserTable')?=?1)
drop?table?[dbo].[SystemKey]
GO

CREATE?TABLE?[dbo].[SystemKey]?(
????[ID]?[int]?NOT?NULL?,
????[KeyName]?[nvarchar]?(50)??NOT?NULL?,
????[KeyValue]?[int]?NOT?NULL?,
????[SourceID]?[nvarchar]?(50)??NOT?NULL?,
????[LockTime]?[datetime]?NULL?
)?ON?[PRIMARY]
GO

KeyName:關鍵字的字段名(我們需要的字段名稱,手工添加到這個表中)

KeyValue:對應字段名的值.

SourceID:字段的來源,如果沒有可以填””

LockTime:鎖定的時間,在程序內部使用.

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2.??? GetKeys方程,通過調用GetKeys得到關鍵字的值.

函數描述如下:

Imports?Microsoft.ApplicationBlocks.Data
Imports?Microsoft.VisualBasic.CompilerServices
Imports?System.Threading
Imports?System.Data.SqlClient
Public?Class?ClassTestClass?ClassTest
????Public?Function?GetKeys()Function?GetKeys(ByVal?KeyName?As?String,?ByVal?Source?As?String,?ByVal?CNString?As?String)?As?Integer
????????Dim?connection?As?New?SqlConnection(CNString)

????????Dim?NewNum?As?Integer
????????Dim?obj2?As?Object
????????Dim?sFlage?As?String?=?"Flag"
????????Try
????????????Dim?sql?As?String
????????????Dim?time?As?DateTime?=?DateAndTime.Now.AddSeconds(1)
????????????connection.Open()
????????????Do?While?(StringType.StrCmp(sFlage,?"",?False)?<>?0)
????????????????sql?=?(("Update?[SystemKey]?Set?[SourceID]='"?&?Source?&?"',?[LockTime]=GetDate()??Where?[KeyName]='"?&?KeyName)?&?"'?AND???((DATEADD(millisecond,?1000,?LockTime)?<GetDate()?)?OR?(?SourceID=''))")
????????????????Dim?j?As?Integer?=?SqlHelper.ExecuteNonQuery(connection,?CommandType.Text,?sql)
????????????????If?(j?>?0)?Then
????????????????????sFlage?=?""
????????????????????Exit?Do
????????????????End?If
????????????????sFlage?=?"Err"
????????????????connection.Close()
????????????????If?(DateTime.Compare(time,?DateAndTime.Now)?<?0)?Then
????????????????????Return?-1
????????????????End?If
????????????????Thread.Sleep(10)
????????????Loop

????????????sql?=?"Select?KeyValue??From?[SystemKey]?Where?[KeyName]='"?&?KeyName?&?"'?AND?SourceID='"?&?Source?&?"'"
????????????Dim?OldNum?As?Object?=?SqlHelper.ExecuteScalar(connection,?CommandType.Text,?sql)
????????????Dim?num?As?Integer?=?(IntegerType.FromObject(OldNum)?+?1)
????????????sql?=?"Update?[SystemKey]?Set?[KeyValue]="?&?StringType.FromInteger(num)?&?",?[SourceID]=''?Where?[KeyName]='"?&?KeyName?&?"'"
????????????SqlHelper.ExecuteNonQuery(connection,?CommandType.Text,?sql)
????????????NewNum?=?num
????????Catch?exception?As?Exception
????????????NewNum?=?-1
????????Finally
????????????If?Not?connection?Is?Nothing?Then
????????????????CType(connection,?IDisposable).Dispose()
????????????End?If
????????End?Try
????????Return?NewNum
????End?Function
End?Class

轉載于:https://www.cnblogs.com/rippleyong/archive/2005/01/31/99892.html

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