Sleeping on the problem!

People are always blaming their circumstances for what they are.
I don’t believe in circumstances. The people who get on in this world are
the people who get up and look for the circumstances they want, and, if they
can’t find them, make them.
‘George BernardShaw’

DB Lab

Today I spent many times designing a database for my database lab project.It’s very hard to Model a part of real world environment for a virtual world application with limited facilities.
ER(Entity Relation) diagram is a good tool but not complete in understanding.
Joe Celko writes in his book(Data and Databases: Concepts in Practice)  :
‘There are several problems with ER modeling:
1.ER does not spend much time on attributes. The names of the columns in a table are
usually just shown inside the entity box, without datatypes. Some products will
indicate which column(s) are the primary keys of the table. Even fewer will use
another notation on the column names to show the foreign keys.

2.Although there can be more than one normalized schema from a single set of
constraints, entities, and relationships, ER tools generate only one diagram. Once
you have begun a diagram, you are committed to one schema design.

3.The diagram generated by ER tools tends to be a planar graph. That means that
there are no crossed lines required to connect the boxes and lines. The fact that a
graph has crossed lines does not make it nonplanar; it might be rearranged to avoid
the crossed lines without changes to the connections

4.ER diagrams cannot express certain constraints or relationships. For example, in the
versions that use only straight lines between entities for relationships, you cannot
easily express an n-ary relationship (n > 2).’

Sleeping On the problem is one of the concepts that i found in theory of management ,It’s very interesting 😀

…………………………….

yesterday was birthday of my brother’s beautiful girl.It was a cold snowy night!
When i first saw the tiny baby with only 2.9 Kilogram weight,i were very excited! it was wonderfull!
Now i am an uncle! i wish the best for my little nice , SABA🙂

SABA

3 thoughts on “Sleeping on the problem!

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