timestamp in .NET

Printer DataMatrix in .NET timestamp

timestamp
Recognizing ECC200 In VS .NET
Using Barcode Control SDK for Visual Studio .NET Control to generate, create, read, scan barcode image in Visual Studio .NET applications.
Encoding Data Matrix In .NET Framework
Using Barcode printer for Visual Studio .NET Control to generate, create Data Matrix image in VS .NET applications.
SQL Server has a timestamp data type. It is used for versioning records in a table. When you insert or update a record in a table with a timestamp field, SQL Server timestamps the change. Figure 9-2 demonstrates such behavior. The table is created with a timestamp field. When a record is inserted, SQL Server automatically sets its value. When the record is updated, SQL Server increases the value of the timestamp.
Scan ECC200 In .NET Framework
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET applications.
Barcode Generator In VS .NET
Using Barcode printer for VS .NET Control to generate, create barcode image in VS .NET applications.
SQL Server 2000 Stored Procedure & XML Programming
Bar Code Reader In Visual Studio .NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in .NET applications.
Make ECC200 In C#.NET
Using Barcode creation for .NET Control to generate, create DataMatrix image in Visual Studio .NET applications.
Figure 9-2
Make Data Matrix 2d Barcode In .NET Framework
Using Barcode generation for ASP.NET Control to generate, create Data Matrix image in ASP.NET applications.
Data Matrix Printer In Visual Basic .NET
Using Barcode generator for VS .NET Control to generate, create Data Matrix 2d barcode image in .NET applications.
Use of the timestamp data type
GS1 DataBar Limited Generation In .NET
Using Barcode maker for Visual Studio .NET Control to generate, create GS1 DataBar Stacked image in .NET applications.
UCC - 12 Generator In .NET
Using Barcode encoder for .NET Control to generate, create UPC-A Supplement 2 image in VS .NET applications.
It is important to realize that timestamp values are not actually a kind of timekeeping. They are just binary values that are increased with every change in the database and, therefore, are unique within the database. You should not make any assumptions about their values and growth. Somebody (or some process) might change something in the database concurrently, and even two changes that you executed consecutively might not have consecutive timestamp values. To make sure that nobody has changed a record in the meantime, you might decide to update it like this:
Paint Code 128C In VS .NET
Using Barcode generator for VS .NET Control to generate, create Code 128 image in VS .NET applications.
Encoding USPS PLANET Barcode In .NET Framework
Using Barcode creation for VS .NET Control to generate, create USPS PLANET Barcode image in VS .NET applications.
update #aTable set description = 'test3' where id = 1 and ts = 0x000000000000007A
Scanning GS1-128 In VB.NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in VS .NET applications.
Bar Code Reader In .NET Framework
Using Barcode Control SDK for ASP.NET Control to generate, create, read, scan barcode image in ASP.NET applications.
-- not a perfect solution
Paint EAN / UCC - 13 In VB.NET
Using Barcode encoder for .NET framework Control to generate, create EAN / UCC - 14 image in .NET applications.
GTIN - 12 Creator In None
Using Barcode encoder for Software Control to generate, create UPC Code image in Software applications.
The record will be updated only if the timestamp is unchanged. The trouble with this solution is that you will not know what happens after the statement is
Code-128 Maker In None
Using Barcode printer for Software Control to generate, create Code 128 image in Software applications.
UPC-A Supplement 2 Generation In None
Using Barcode encoder for Word Control to generate, create UPC-A Supplement 2 image in Office Word applications.
9: Advanced Stored Procedure Programming
Painting ECC200 In Java
Using Barcode printer for Java Control to generate, create DataMatrix image in Java applications.
Linear Barcode Generator In Visual Basic .NET
Using Barcode generator for Visual Studio .NET Control to generate, create Linear 1D Barcode image in .NET framework applications.
executed. Maybe everything is okay and the record has been successfully changed. It is possible that the record was not updated because the timestamp was changed, but it is also possible that the record is not in the table any more.
TSEqual() Function
The SQL Server TSEqual() function (no longer described in SQL Server Books Online) compares timestamp values in the table and the Transact-SQL statement (see Figure 9-3). If they do not match, this function raises an error 532 and aborts the statement. This function allows you to write code that handles errors properly (for example, the user can be prompted for further action). If you executed the previous Update statement, the following one should cause SQL Server to force an error:
update #aTable set description = 'test4' where id = 1 and TSEQUAL(ts, 0x000000000000007A)
Figure 9-3
The use of the TSEqual() function
SQL Server 2000 Stored Procedure & XML Programming
You can use this function in stored procedures to implement optimistic locking:
Create Procedure prUpdateContact_1 -- update record from contact table -- prevent user from overwriting changed record ( @intContactId int, @chvFirstName varchar(30), @chvLastName varchar(30), @chvPhone typPhone, @chvFax typPhone, @chvEmail typEmail, @insOrgUnitId smallint, @chvUserName varchar(50), @tsOriginal timestamp ) As Set nocount on Update Contact Set FirstName = @chvFirstName, LastName = @chvLastName, Phone = @chvPhone, Fax = @chvFax, Email = @chvEmail, OrgUnitId = @insOrgUnitId, UserName = @chvUserName Where ContactId = @intContactId and TSEQUAL(ts, @tsOriginal) Return @@Error
You will have no problem executing this code from Transact-SQL:
Declare @intErrorCode int Exec @intErrorCode = prUpdateContact_1 1, 'Dejan', 'Sunderic', '121-1111', '111-1112', 'dejans@hotmail.com', 1, 'dejans', 0x00000000000009C3 Select @intErrorCode ErrorCode
Unfortunately, some versions of client development tools (for example, Visual Basic) and some data access methods (for example, RDO and ADO) have problems retrieving and using timestamp values.
9: Advanced Stored Procedure Programming
Before you implement 50 stored procedures in this manner, you should test whether your client development tools support timestamp values. If they do not, you must implement a workaround.
timestamp Conversion
The first workaround that comes to mind is to pass the timestamp as some other data type. Binary(8) and varchar are the first options most people try. Unfortunately, client tools usually do not support binary data types either. The trouble with varchar is that SQL Server converts the timestamp to an empty string. One solution that works is based on the conversion of the timestamp to a datetime or money data type (sounds strange, doesn t it ). Conversion in the opposite direction results in the same timestamp as well. You can test this workaround using the following code:
declare @dtmOriginal datetime, @tsOriginal timestamp Set @tsOriginal = 0x00000000000009C3 select @dtmOriginal = Convert(datetime, @tsOriginal) select @dtmOriginal, Convert (timestamp, @dtmOriginal)
Copyright © OnBarcode.com . All rights reserved.