hi

i would like to give each record in my application a uniqe identifier how
can i generate it ? how to use system.guid to generate ?

Hi,

Thanks for your post.

What's your programming language? Here I use C# to demostrate guid
generation:

Guid g = Guid.NewGuid();
string guid = g.ToString();

How many records will be generated in your application? Although it is very
rare to happen that two generated guids are same. But if it has millions or
billions of generated records. It does have chances that two records has
same guid. Please take it into your consideration in your application.

Another way to keep that ID unique is to use incremental identifier, which
is widely used in database. To implement it by setting a integer or double
indentifier and increment it by 1 for every new record. This way has the
benifit that it saves memory and no duplication compared with guid.
However, it has limit of the length of its Type. For example, int's max
value is 2,147,483,647.

Please let me know if you need more information about it. Thanks.

Best Regards,
Hongye Sun (hongyes (AT) online (DOT) microsoft.com, remove 'online.')
Microsoft Online Community Support

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hi

i use VB.Net

so this incremental identifier will it be unique in all records in all
tables of an application ?
cause the incremental i know is unique in one table only ?

also how to use unique identifier in Vb

regards



"Ammar S. Mitoori" wrote:

Hi Ammar,

Thanks for your reply.

Here is the code sample to use GUID in VB.net

Dim g As Guid = Guid.NewGuid()
' Generate GUID string
Dim guidStr As String = g.ToString()
' Generate GUID byte array
Dim guidByte As Byte() = g.ToByteArray()

Are you using database in your application? If yes, to use incremental ID
in all records, usually, we use a table which is responsible to generate
unique id for all other records. The ID table only has one incremental ID
column. Every time a new record is created, we insert one item in ID table
and get its ID to assign it to the new record.

Thanks,
Hongye Sun (hongyes (AT) online (DOT) microsoft.com, remove 'online.')
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
msdnmg (AT) microsoft (DOT) com.

This posting is provided "AS IS" with no warranties, and confers no rights.

thanks for the replay

but how can i get the value of the last record in that ID table
can you suggest some VB.NET code please ?

Regards

""Hongye Sun [MSFT]"" wrote:

Hi Ammar,

In order to generate global ID from one table, you can:
1. Create one table GID with only one colume ID:

CREATE TABLE [dbo].[GID](
[ID] [bigint] IDENTITY(1,1) NOT NULL,
CONSTRAINT [PK_GID] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY =
OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

2. Write following function to insert and get MAX id from table:

Public Function NewSequenceId()
Dim myConnection As SqlConnection
Dim myCommand As SqlCommand
Dim dr As SqlDataReader
Dim id As Long
myConnection = New SqlConnection("<Replace with your connection
string")
Try
myConnection.Open()
'opening the connection
myCommand = New SqlCommand("INSERT INTO GID DEFAULT VALUES",
myConnection)
myCommand.ExecuteNonQuery()

myCommand.CommandText = "SELECT MAX(ID) FROM GID"

'executing the command and assigning it to connection
dr = myCommand.ExecuteReader()
dr.Read()
id = dr.GetInt64(0)
Catch e As Exception
Finally
dr.Close()
myConnection.Close()
End Try

Return id
End Function

The return value is a long type value which is global unique.

I found a TSQL method which can generate GUID which is bigger than the last
GUID. This method avoid duplicate possiblities. Please read the link below:
http://msdn.microsoft.com/en-us/library/ms189786.aspx

Sincerely,
Hongye Sun (hongyes (AT) online (DOT) microsoft.com, remove 'online.')
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
msdnmg (AT) microsoft (DOT) com.

This posting is provided "AS IS" with no warranties, and confers no rights.

Hi Ammar,

Is this issue resolved? Please let me know what else I can help.

Sincerely,
Hongye Sun (hongyes (AT) online (DOT) microsoft.com, remove 'online.')
Microsoft Online Community Support

Delighting our customers is our #1 priority. We welcome your comments and
suggestions about how we can improve the support we provide to you. Please
feel free to let my manager know what you think of the level of service
provided. You can send feedback directly to my manager at:
msdnmg (AT) microsoft (DOT) com.

This posting is provided "AS IS" with no warranties, and confers no rights.