I’ve just replied to a question in dotnethell italian forum about the topic in the title. Actually it’s not the first time I got this kind of question:
“How can I repeat a row using a value that is stored in another column of the same table?”
Ok, let’s describe a solution step by step.
Usually I found some questions on the forums about that topic. For instance:
- “WHERE or HAVING?”
- “Is the ON clause more efficient than the WHERE clause?”
- “Why the field aliases cannot be used with the GROUP BY clause?”
These three questions are syntax oriented. Actually there are a lot of requests about subqueries, temporary objects, sort operations and so on. This kind of questions can be replied reading this logical process document (pdf)
. I love it and I share it everywhere, also when training in classes/on the job.
It is a LOGICAL workflow used by the Query Processor in order to generate the related PHYSICAL process for retrieving data.