Answer:
The answer to this question is given below in this explanation section.
Explanation:
In the relationship model of database a primary key is a specific choice of a minimal set of attributes that uniquely specific a tuple in a relation.Informally a primary key is which attribute and in simple cases are simple a single attribute.More formally a primary key is a choice of candidate key any other candidate key is an alternate key.
A primary key may consists of real word observable in which way it is called natural key,while an attribute created to function as a key and not use for identification outside the database is called a surrogate key.For example for a database of people time and location of birth could be a natural key.National identification number is another example of an attribute that may be used as an natural key.
True cause sometimes it can delete all ur work
Answer:
To make a computer more secure
Explanation:
we have following ways :
1)we should have anti virus to protect our computer.
2)we should not play or look computer for a long time because it destroy our files
Answer:
Explanation:
Explicit Dependencies
<u>It states that the classes and methods should explicitly require , via constructor or method parameters all the collaborating objects that are required for the function to work properly .</u>
Classes with the implicit dependencies cost very high for the maintenance than the explicit dependencies .
Even , the implicit dependencies are difficult to test as they are tightly coupled to their collaborators .
Answer:
it means that they can charge companies to come mine it making them more wealthy they can also upscale the materials needed to make it as they are the only countries that sell it so they have no one to compete with
