In part 5 of this series we examined a couple of examples where you had to handle the “first child first” rule with a little care. In part 6 we continue this exploration to look at a general principle – the “pushed subquery” – where the “first child first” could lead you to the wrong conclusion. Access or Filter If… Read more
I’ve offered up “first child first, recursive descent” as a basic strategy for interpreting execution plans – but it’s not a perfect rule, and it can be easy to lose track of what’s going on even when the basic “first child first” is being obeyed. In this article we’ll be looking at a couple of examples where we will st… Read more
When a database starts showing signs of an illness, it's up to the DBA to get to the root of the problem, fast. Kat Hicks takes a look at the most common causes of database troubles, free tools that can help, and the misconceptions that get in the way. … Read more
Subqueries and derived tables can add great versatility to SQL statements, cut down complexity, but can occasionally be a curse when their effect on performance is poorly understood. Surely everyone understands the various types of subqueries and how they are used? If you felt a twinge of doubt, here is Rob Sheldon's easy guide to the subject.
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