NULLs in SQL are a mixed blessing. The Three-Valued Logic of SQL has its uses but can cause difficulties to anyone who assumes that NULL has a 'value'. It can make reports go horribly wrong in a number of alarming ways, as Robert Sheldon explains.… Read more
One of the times that you need things to go right is when you are doing analysis and reporting. This is generally based on time and date. A sure-fire way of getting managers upset is to get the figures horribly wrong by messing up the way that you handle datetime values in SQL Server. In the interests of peace, harmony and a long career in BI, Robert Sheldon outlines some of the worst mistakes you can make when using SQL Server dates.… Read more
It is no good doing some or most of the aspects of SQL Server security right. You have to get them all right, because any effective penetration of your security is likely to spell disaster. If you fail in any of the ways that Robert Sheldon lists and describes, then you can't assume that your data is secure, and things are likely to go horribly wrong.… Read more
One of the most certain ways of going wrong with any relational database is to get data conversion wrong. Implicit data conversion is a good feature for the expert but can cause a lot of trouble to the unwary. These boil down to seven ways of failing to get data conversion right. Rob Sheldon explains and gives sage advice on how to avoid the problems… Read more
Database Design is one of those tasks where you have to carefully get all the major aspects right. If you mess-up just one of these, it can all go horribly wrong. So what are these aspects that can ruin database design, and how can you get them right? Robert Sheldon explains.… Read more
ETL ( Extract, transform, load) doesn't have to be like a spell on hell. To make a success of ETL systems, you need the freedom and ability to make graceful U-turns when you detect a mistake in architecture or configuration: to fix the root problem rather than to merely tackle the symptoms. Feodor lists the eight most common root causes of failure in ETL systems, and how to fix them.… Read more
