Too often, the batch systems that underlie a lot of database processing just grow without conscious design. When runs start to extend beyond their allotted time, and tuning no longer solves the problem, it is often discovered that batches are run in series, with draconian error handling. It is time to impose some rational design, and Nigel is a seasoned healer of batch processes.… Read more
SQL Server filtered indexes can save space and improve performance if they are used properly. Under what circumstances can they be used? When are they most effective, and what sort of performance gain or space-saving is likely? How does a filtered index affect the choice of execution plan? Seth explores these questions with practical experiments… Read more
Accurate statistics about the data held in tables are used to provide the best execution strategy for SQL queries. but if the statistics don't accurately reflect the current contents of the table you'll get a poorly-performing query. How do you find out if statistics are correct, and what can you do if the automatic update of statistics isn't right for the way a table is used? … Read more
Normally, the query Optimiser won't consider 'bushy' plans, where both operands to a join operator could be intermediate results from other joins. This means that it won't produce good query plans for some types of query. Hints, by themselves won't do it. More powerful magic is required.… Read more
The performance of 'extract, transform, load' (ETL) processes for large quantities of data can always be improved by objective testing and experiment with alternative techniques. The cause of poor performance can sometimes be surprising.… Read more
If you need to optimise SQL Server performance, it pays to understand SQL Server Statistics. Grant Fritchey answers the 18 most frequently-asked questions about SQL Server Statistics: the ones we somehow feel silly asking in public, and think twice about doing so.… Read more
It is frustrating when you hit 'submit' and you get the hourglass big-time. Is it the database to blame? It could be, but there are other suspects that should be considered. Feodor describes where, in the long route, to and fro', that a data request makes before returning, that things can get snarled up.… Read more
SQL Server Indexes need to be effective. It is wrong to have too few or too many. The ones you create must ensure that the workload reads the data quickly with a minimum of I/O. As well as a sound knowledge of the way that relational databases work, it helps to be familiar with the Dynamic Management Objects that are there to assist with your indexing strategy.… Read more
There are several reliable indications, using SQL Queries, of the what is causing SQL Server performance problems. Some of these are fairly obvious, but others aren't. Grant shows how you can get clues from any SQL Server as to the cause of stress.… Read more
There are seven common antipatterns in TSQL coding that make code perform badly, and three good habits which will generally ensure that your code runs fast. If you learn nothing else from this list of great advice from Grant, just keep in mind that you should 'write for the optimizer'.… Read more
Alex's team of developers are geared to doing rapid development of database applications in a busy corporate setting, yet take considerable time over meticulous database design, extensive constraints, automated tests, error logs, and defensive coding. Why? Because it cuts down on the subsequent need for maintenanc… Read more
Prefetching can make a surprising difference to SQL Server query execution times where there is a high incidence of waiting for disk i/o operations, but the benefits come at a cost. Mostly, the Query Optimizer gets it right, but occasionally there are queries that would benefit from tuning. … Read more
Three SQL Server MVPs, and stalwarts of the SQLServerCentral and MSDN community forums, provide fascinating insight into the most common SQL Server problems, why they occur, and how they can be diagnosed using tools such as Performance Monitor, Dynamic Management Views and server-side tracing. The focus is on practical solutions for removing root causes of these problems, rather than "papering over the cracks".… Read more
When healing a sick SQL Server, you must forget the idea that there could ever be a simple correspondence between symptom and disease: The art of troubleshooting is much more the art of discovering, and assembling, the various pieces of the puzzle so that you have a complete understanding of what is going on inside of a server… Read more
As WPF and Silverlight sit on the .NET framework, they're subject to the rules of the Garbage Collector. That means there are a few unique ways in which WPF will cause your application to leak memory, and Chris Farrell points out the most prominent culprits.… Read more
.NET Memory management is an impressive and comprehensive system, but it's not flawless, and it's occasionally a little anti-intuitive. As a result, there are a few common misconceptions which need to be dispelled before you can really get the most out of the .NET framework.… Read more
It is dangerous to assume that your data is sound. SQL already has intrinsic ways to cope with missing, or unknown data in its comparison predicate operators, or Theta operators. Can SQL be more effective in the way it deals with data quality? Joe Celko describes how the SQL Standard could soon evolve to deal with data in ways that allow aggregation and windowing in cases where the data quality is less than perfect
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Since the introduction of SQL Server 2005, there is a simple lightweight trace that is left running by default on every SQL Server. This provides some very valuable information for the DBA about the running server, but it isn't well-documented. Feodor reveals many of the secrets of this facility and shows how to get reports from it.
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Once, when disk space was at a premium, DBAs fought hard to keep the size of their database down. Now there seems less motivation to 'fight the flab' of a database. Fabiano Amorim was watching television recently when the subject matter, cosmetic surgery, gave him the theme and inspiration for this guide to keeping your database fit and trim.
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The UNION, EXCEPT and INTERSECT operators of SQL enable you to combine more than one SELECT statement to form a single result set. The UNION operator returns all rows. The INTERSECT operator returns all rows that are in both result sets. The EXCEPT operator returns the rows that are only in the first result set but not in the second. Simple? Rob Sheldon explains all, with plenty of examples… Read more
