Welcome!

Microsoft Cloud Authors: Pat Romanski, Elizabeth White, Liz McMillan, Mihai Corbuleac, David Bermingham

Related Topics: Microsoft Cloud

Microsoft Cloud: Article

A Summary of T-SQL Enhancements in SQL Server 2005

Taking a closer look at the updated features

Microsoft is releasing a new version of SQL Server after a gap of five years. This version (SQL Server 2005) introduces a horde of new attention-grabbing features like native XML storage and querying (using XQuery), CLR integration, SQL Web Services, query notifications, and the Service Broker. Apart from these high-profile enhancements, SQL Server 2005 also comes with improved T-SQL support.

Overview of T-SQL Enhancements
Most of SQL Server 2005's T-SQL enhancements focus on offering greater expressiveness to queries. We will look at each of these individual enhancements in detail. The list of enhancements includes:

  • Relational operators
  • TOP
  • Recursive queries
  • XML showplan
  • Snapshot isolation level
  • Data types
  • DDL triggers
  • DML with output
  • Exception handling
Relational Operators
SQL Server 2005 introduces three new relational operators: PIVOT, UNPIVOT, and APPLY.

The PIVOT operator is very similar to the TRANSFORM operator that Microsoft Access provides. It is used to rotate rows into columns. The best way to learn about PIVOT is through an example (see Figure 1).

This table lists the sales of a Toyota dealership. Notice that some models have more than one row for a particular year. Now we apply the following SELECT query (which uses the PIVOT operator) to the SalesSummary table. The result we get is shown in Figure 2.

SELECT *
FROM [SalesSummary]
PIVOT (SUM ([UnitsSold]) FOR [Year] IN ([2003], [2004])) AS [T]

The table was PIVOTed on the year column. Notice how the unique year values have taken the shape of columns and the corresponding number of units sold have been summed up.

The UNPIVOT operator does the opposite of what PIVOT does - it rotates columns into rows. Let's say we want to rotate the table in Figure 2 (let's call it Year WiseSalesSummary), so that the number of units sold is displayed for each year. All we have to do is apply the following SELECT query. The result of the UNPIVOT operation is shown in Figure 3.

SELECT *
FROM [YearWiseSalesSummary]
UNPIVOT (UnitsSold FOR [Year] in ([2003], [2004])) AS T

The APPLY is another new operator available in SQL Server 2005. When used in the FROM clause, it invokes a table-valued UDF for each row of a table. The UDF can optionally use the columns of the table as arguments.

Let's say we have a table called StudentScores that has the Math, Physics, and Chemistry scores of a bunch of students (see Figure 4).

Now, create the Calculate-Grade function, which takes the subject scores of each of the student one at a time and returns the grade of the student.


CREATE FUNCTION [CalculateGrade] 
(@math AS INT, @physics AS INT, @chemistry AS INT)
RETURNS  @GradeTable TABLE ([Grade] CHAR (1))
AS
BEGIN
	DECLARE @average FLOAT
	SET @average = (@math + @physics + @chemistry) / 3
	IF @average >= 90
		INSERT INTO @GradeTable VALUES ('A')
	ELSE IF @average >=80
		INSERT INTO @GradeTable VALUES ('B')
	ELSE IF @average >=70
		INSERT INTO @GradeTable VALUES ('C')
	ELSE
		INSERT INTO @GradeTable VALUES ('F')
	RETURN
END

The following query uses the APPLY relational operator to apply the CalculateGrade function on every row of the StudentScores table. We also pass the Math, Physics, and Chemistry scores to the CalculateGrade function.

SELECT [Name], I.Grade
FROM [StudentScores] AS O
CROSS APPLY CalculateGrade ([Math], [Physics], [Chemistry]) AS I

Figure 5 is an illustrative example of the APPLY operator. There are several ways (many of them better than using the APPLY operator) to achieve the same result.

TOP
In SQL Server, a SELECT query can use the TOP option to specify the number of rows that should be returned. The argument to TOP was a constant value of type BIGINT. The TOP option can also be qualified with the PERCENT keyword to specify that a percentage of the total number of rows should be returned by a SELECT query. The argument in this case was a constant value of type FLOAT.

In SQL Server 2005, an argument can be specified using an expression or a query, the only condition being that both should result in a value that is of the correct type.

For example, the following query returns the latest 10 orders from the Orders table in the Northwind database.

DECLARE @NO_OF_ROWS BIGINT
SET @NO_OF_ROWS = 10

SELECT TOP (@NO_OF_ROWS)
*
FROM [Orders]
ORDER BY [OrderDate] DESC

In SQL Server 2005, the TOP keyword can also be used with INSERT, UPDATE, and DELETE commands. Using TOP to do batch inserts, updates, or delete is more optimal than using the older SET ROWCOUNT method.

An example of using TOP with the DELETE operator would be the following query, which purges the oldest 10,000 rows from TempTable.

DELETE TOP (10000)
FROM [TempTable]
ORDER BY [TimeStamp]

Recursive Queries
SQL Server 2005 introduces Common Table Expressions (CTEs) that allow you to write named table expressions that persist for the duration of a query. The functionality of CTEs is somewhere between derived tables and views.

A CTE can be defined by using the WITH clause, as shown in the following code.

WITH CustomerSales ([CustomerId, [TotalSales])
AS
(
SELECT
[CustomerId], SUM ([UnitPrice] * [Quantity] * (1 - [Discount]))
AS [TotalSales]
FROM [Orders] AS [O] INNER JOIN
[Order Details] AS [OD]
ON [O].[OrderId] = [OD].[OrderId]

GROUP BY [CustomerId]
)
SELECT * FROM [CustomerSales]

This query creates a non-recursive CTE called CustomerSales that has two columns: CustomerId and TotalSales. The CTE gets all unique customer ids and the total sales made to them.

The primary purpose of having CTEs is to support recursion. Recursive CTEs improve readability and manageability of complex SQL statements. Recursive CTEs have the ability to traverse recursive hierarchies in a single query. A typical scenario where one would use a recursive CTE would be when a table has a self-referential constraint.

The recursive form of a CTE is as shown:

<Non-recursive SELECT>
UNION ALL
<SELECT referencing the CTE>

The recursion terminates when the second SELECT block produces an empty result.

The following recursive CTE prints out the name of all employees and their managers found in the Northwind database. The results are shown in Figure 6.


WITH EmployeeManagerCTE ([EmployeeId], [EmployeeName], [ManagerName])
AS
(
	SELECT 
		[EmployeeId], 
		[LastName] + ', ' + [FirstName], 
		[LastName] + ', ' + [FirstName] 
	FROM employees 
	WHERE [ReportsTo] IS NULL

	UNION ALL

	SELECT 
		[E1].[EmployeeId], 
		[E1].[LastName] + ', ' + [E1].[FirstName], 
		[E2].[EmployeeName]
	FROM [Employees] [E1] INNER JOIN 
	[EmployeeManagerCTE] [E2]
	ON [E1].[ReportsTo] = [E2].[EmployeeId]

)
SELECT * FROM [EmployeeManagerCTE]

XML Showplan
SQL Server 2005 has the facility to output a query plan as XML that uses a documented XML schema and carries more information than SQL Server 2000 textual or graphical formats.

The XML query plan output lends itself to various kinds of advanced processing with XQuery, XSLT, DOM, and the CLR.

Snapshot Isolation Level
SQL Server 2000 supports four isolation levels: read uncommitted, read committed, repeatable read, and serializable. SQL Server 2005 introduces a new snapshot isolation level. The snapshot isolation level is based on optimistic concurrency. It holds onto a snapshot of committed data from when the transaction started, allowing non-blocking reads to take place.

Data Types
SQL Server 2005 introduces a few new data types: XML, VARCHAR (MAX), NVARCHAR (MAX), and VARBINARY (MAX).

The XML data type is a first-class data type in SQL Server 2005 and can be used to define columns, variables, and parameters for stored procedures and user-defined functions. The XML data type can be optionally constrained by an XML schema. SQL Server 2005 also provides built-in XQuery support to query XML data.

The VARCHAR (MAX), NVARCHAR (MAX), and VARBINARY (MAX) data types can store up to 2GB of data and provide alternatives to the existing TEXT, NTEXT, and IMAGE data types respectively.

DDL Triggers
SQL Server 2005 has extended traditional triggers and enabled them to be fired for DDL operations like CREATE, ALTER, and DROP. These triggers are created, altered, and dropped using similar Transact-SQL syntax as that for standard triggers.

DDL triggers apply to all commands of a single type across a database or server and they execute only after completion of a DDL statement (although they can roll back the transaction to before the execution of the DDL statement that caused their triggering). DDL triggers cannot be INSTEAD OF triggers.

DDL triggers help to enforce development rules and standards for objects in a database; protect from accidental drops; help in object check-in/checkout, source versioning, and log management activities.

An example of a DDL trigger that prevents the dropping of a table is as shown:

CREATE TRIGGER OnDropTable ON DATABASE FOR DROP_TABLE
AS
    RAISERROR ('No drops allowed', 10, 1)
ROLLBACK

DML with Output
SQL Server 2005 introduces the OUTPUT clause that returns inserted, updated, or deleted rows as part of a DML operation. The OUPUT clause can be used with INSERT, DELETE, and UPDATE statements. The "DELETED" and "INSERTED" pseudo-tables can be used to get the pre- and post-operation values.

An example usage is as follows:

UPDATE [Jobs]
SET [Status] = 'Done'
OUTPUT DELETED.*, INSERTED.*
WHERE [Status] = 'In progress'

The DELETED values are not available for INSERT operations while the INSERTED values are not available for the DELETE operations. Both the INSERTED and the DELETED values are available for UPDATE operations.

Exception Handling
Exception handling can now be done in SQL Server 2005 by using the very well-known TRY/CATCH paradigm. All errors that set the @@error variable will now throw exceptions. The syntax of using exception handling is as follows:

BEGIN TRY
    -- SQL statements
END TRY
BEGIN CATCH
    -- SQL statements
END CATCH

TRY/CATCH blocks can also be nested. Error details are available inside the CATCH block through a set of functions - error_number (), error_message (), error_severity (), and error_state (). RAISERROR can be used to re-throw and exception from within a CATCH block.

Conclusion
SQL Server 2005 enhances T-SQL on a number of fronts - it introduces new and important data types, brings more power and expressiveness to SQL querying, provides more procedural capabilities, and improves parallelism.

More Stories By Mujtaba Syed

Mujtaba Syed works as a software architect with Marlabs Inc. He is an MCSD
(early achiever) and loves to speak about and write on Microsoft .NET. Mujtaba has been programming the Microsoft .NET Framework since its beta 1 release. His current interests are focused on Longhorn.

Comments (3) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
CuriousTom 10/11/07 03:25:06 PM EDT

Good One

sudhakar 08/28/04 05:58:42 AM EDT

Sorry, i take back my words.

I could find the images, it would have been better to embed the images in the article instead of providing links to them at the end of it.

sudhakar 08/28/04 05:36:01 AM EDT

I didnt find any figures (which have been refered) in this article which made the examples given for each feature quite difficult to understand. The pictorial representation of query results would have been very helpful.

Pls. send me an alert to my mailid if you update this article with relevent figures.

@ThingsExpo Stories
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
SYS-CON Events announced today that ReadyTalk, a leading provider of online conferencing and webinar services, has been named Vendor Presentation Sponsor at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. ReadyTalk delivers audio and web conferencing services that inspire collaboration and enable the Future of Work for today’s increasingly digital and mobile workforce. By combining intuitive, innovative tec...
Amazon has gradually rolled out parts of its IoT offerings, but these are just the tip of the iceberg. In addition to optimizing their backend AWS offerings, Amazon is laying the ground work to be a major force in IoT - especially in the connected home and office. In his session at @ThingsExpo, Chris Kocher, founder and managing director of Grey Heron, explained how Amazon is extending its reach to become a major force in IoT by building on its dominant cloud IoT platform, its Dash Button strat...
Connected devices and the industrial internet are growing exponentially every year with Cisco expecting 50 billion devices to be in operation by 2020. In this period of growth, location-based insights are becoming invaluable to many businesses as they adopt new connected technologies. Knowing when and where these devices connect from is critical for a number of scenarios in supply chain management, disaster management, emergency response, M2M, location marketing and more. In his session at @Th...
The cloud market growth today is largely in public clouds. While there is a lot of spend in IT departments in virtualization, these aren’t yet translating into a true “cloud” experience within the enterprise. What is stopping the growth of the “private cloud” market? In his general session at 18th Cloud Expo, Nara Rajagopalan, CEO of Accelerite, explored the challenges in deploying, managing, and getting adoption for a private cloud within an enterprise. What are the key differences between wh...
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his Day 2 Keynote at @ThingsExpo, Henrik Kenani Dahlgren, Portfolio Marketing Manager at Ericsson, discussed how to plan to cooperate, partner, and form lasting all-star teams to change t...
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
industrial company for a multi-year contract initially valued at over $4.0 million. In addition to DataV software, Bsquare will also provide comprehensive systems integration, support and maintenance services. DataV leverages advanced data analytics, predictive reasoning, data-driven diagnostics, and automated orchestration of remediation actions in order to improve asset uptime while reducing service and warranty costs.
Vidyo, Inc., has joined the Alliance for Open Media. The Alliance for Open Media is a non-profit organization working to define and develop media technologies that address the need for an open standard for video compression and delivery over the web. As a member of the Alliance, Vidyo will collaborate with industry leaders in pursuit of an open and royalty-free AOMedia Video codec, AV1. Vidyo’s contributions to the organization will bring to bear its long history of expertise in codec technolo...