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Author Question: To build an information system, which one do you need to identify first classes or objects? What ... (Read 23 times)

khang

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on: Jul 7, 2018
To build an information system, which one do you need to identify first classes or objects?
 
  What will be an ideal response?

Question 2

Explain foreign keys are they necessary?
 
  What will be an ideal response?


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Melissahxx

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Reply #1 on: Jul 7, 2018
Answer to Question 1

The process of classification  that is, definition of classes  starts with a concept: a general idea that is shaped into a distinct class through a mental and semantic process of generalization. In other words, the concept always precedes classification, regardless of whether existing objects give rise to a class or the objects are created from a class.

Answer to Question 2

The relationship between entities in different tables is established through foreign keys. The foreign key is an attribute in one table, the value of which must match the value of a primary or an alternate key in another table. Unlike primary keys, foreign keys are not required and do not, necessarily, identify a row uniquely. Like primary keys, a foreign key can be composite, consisting of more than one attribute.


khang

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Reply 2 on: Jul 7, 2018
:D TYSM

dreamfighter72

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Reply 3 on: Yesterday
YES! Correct, THANKS for helping me on my review

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