Sometimes we work on systems where a hierarchical data structure exists on some entities like employees and their managers. Both employees and managers can be called employees but there is a self join relation between them as each employee must have a manager. We all faced the situation when we need to get the info about each employee and his/her direct manager. At this point we used to join between the employees (child) table and itself (parent) on the condition that the parent id of the child is equal to the id of the parent. This is good. But, what about if we need to get the hierarchical tree of managers of a certain employee not just his direct manager. It seems as we just need to the same join but more than one time till we are up all the way to the head manager. This is somehow logical but how can we do this number of joins and we don't know the number of levels up to the head manager?!!! If you want to know more, you can read this article.
4. Sometimes we work on systems where a hierarchical data structure exists on some entities
like employees and their managers. Both employees and managers can be called employees
but there is a self join relation between them as each employee must have a manager. We
all faced the situation when we need to get the info about each employee and his/her direct
manager. At this point we used to join between the employees (child) table and itself
(parent) on the condition that the parent id of the child is equal to the id of the parent. This
is good. But, what about if we need to get the hierarchical tree of managers of a certain
employee not just his direct manager. It seems as we just need to the same join but more
than one time till we are up all the way to the head manager. This is somehow logical but
how can we do this number of joins and we don't know the number of levels up to the head
manager?!!! If you want to know more, you can read this article.
[Development Simply Put] How To Apply
Recursive SQL Selections On Hierarchical Data
"If you can't explain it simply, you don't understand it well
enough" -Albert Einstein
5.
6. I am "Ahmed Tarek" the owner and author of the "Development Simply Put" blog. During my career
days and day after day I got more confident that it's all about sharing not the title you have. I believe
that everyone has something to share whatever small he thinks of it. Sometimes a great idea comes
out of just a tiny idea and the same for knowledge. I always try to gain knowledge and learn new skills
and I found that the best way to learn is to try to teach what you already know. This makes you think
of the best simplest way to explain complex logic which makes you spot some points may be even
yourself didn't recognize in the first time.
The greatest thing in the human mind is that it carries out too complicated operations and finally
presents it into a simple form, so why do we always try to re-complicate things? This is what
encouraged me to start my blog -Development Simply Put
(http://developmentsimplyput.blogspot.com)- trying to do my best to simplify main concepts in IT
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"If you can't explain it simply, you don't understand it well
enough" -Albert Einstein
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"If you can't explain it simply, you don't understand it well
enough" -Albert Einstein