下面将为您介绍通过程序获得SQL Server自增型字段的函数--GetKey函数的方法，供您参考，希望对你更好学习SQL中函数能够有所帮助。
概述:
通过程序来产生自增型字段,可以避免多用户操作的读取脏数据,操作也很简便.可以更好的在程序中控制这些关键字段的数值.
关键步骤:
1. 创建用于存放需要自增的数据表.(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:关键字的字段名(我们需要的字段名称,手工添加到这个表中)
KeyValue:对应字段名的值.
SourceID:字段的来源,假如没有可以填””
LockTime:锁定的时间,在程序内部使用.
2. GetKeys函数方程,通过调用GetKeys函数得到关键字的值.
函数描述如下:
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