Datasheet

20
Chapter 1: Introducing T-SQL and Data Management Systems
Bulk Update Locks
A bulk update lock on a table allows multiple bulk load threads to load data into a table while
preventing other types of data access. Bulk update locks are issued when table locking is enabled at the
table or the chosen as an option with the bulk operation.
Key Range Locks
Key - range locks protect a range of rows implicitly included in a record set being read by a Transact - SQL
statement while using the serializable transaction isolation level. The serializable isolation level requires
that any query executed during a transaction must obtain the same set of rows every time it is executed
during the transaction. A key range lock protects this requirement by preventing other transactions from
inserting new rows whose keys would fall in the range of keys read by the serializable transaction.
SQL Server and Other Products
Microsoft has plenty of competition in the client/server database world and SQL Server is a relatively
young product by comparison. However, it has enjoyed wide acceptance in the industry due to its ease
of use and attractive pricing. If our friends at Microsoft know how to do anything exceptionally well, it ’ s
taking a product to market so it becomes very mainstream and widely accepted.
Microsoft SQL Server
Here is a short history lesson on Microsoft ’ s SQL Server. Originally, SQL Server was a Sybase product
created for IBM ’ s OS/2 platform. Microsoft engineers worked with Sybase and IBM but eventually
withdrew from the project. Then, Microsoft licensed the Sybase SQL Server code and ported the product
to work with Windows NT. It took a couple of years before SQL Server really became a viable product.
The SQL Server team went to work to create a brand new database engine using the Sybase code as a
model. They eventually rewrote the product from scratch.
When SQL Server 7.0 was released in late 1998, it was a major departure from the previous version, SQL
Server 6.5. SQL Server 7.0 contained very little Sybase code with the exception of the core database
engine technology, which was still under license from Sybase. SQL Server 2000 was released in 2000 with
many useful new features, but was essentially just an incremental upgrade of the 7.0 product. SQL
Server 2005, however, is a major upgrade and some say it’s the very first completely Microsoft product.
Any vestiges of Sybase are long gone. The storage and retrieval engine has been completely rewritten,
the .NET Framework has been incorporated, and the product has significantly risen in both power and
scalability. SQL Server 2008 is to SQL Server 2005 what SQL Server 2000 was to SQL Server 7.0. There are
some very interesting and powerful improvements to the server, which we will address in the coming
chapters, but the changes are not as dramatic as the changes that SQL Server 2005 brought.
Oracle
Oracle is probably the most recognizable enterprise - class database product in the industry. After IBM ’ s
E. F. Codd published his original papers on the fundamental principles of relational data storage and
design in 1970, Larry Ellison, founder of Oracle, went to work to build a product to apply those
principles. Founded in 1977, Oracle has had a dominant place in the database market for quite some time
with a comprehensive suite of database tools and related solutions. Versions of Oracle run on UNIX,
Linux, and Windows server operating systems.
CH001.indd 20CH001.indd 20 3/26/10 11:35:42 AM3/26/10 11:35:42 AM