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Q:

Which among the following keys are used to identify each row of the table uniquely?

A) Primary key B) Unique key
C) Partial key D) None of the above
 
Answer & Explanation Answer: A) Primary key

Explanation:

Primary key helps us to identify a row uniquely in a relation

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Q:

A school committee of 5 is to be formed from 12 students.How many committees can be formed if John must be on the committee?

A) 11P4 B) 11C4
C) 11P5 D) 11C5
 
Answer & Explanation Answer: B) 11C4

Explanation:

If John must be on the committee,we have 11 students remaining,out of which we choose 4. So,11C4

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Q:

If there are 17 randomly placed dots on a circle,how many lines can you form using any 2 dots?

A) 126 B) 130
C) 136 D) 120
 
Answer & Explanation Answer: C) 136

Explanation:

17C2 = 136 (combination)

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Q:

How many ways can you select 17 songs for mix CD out of possible 38 songs?

A) 2878 B) 2878 x 10^2
C) 290183753 D) 2878 x 10^10
 
Answer & Explanation Answer: D) 2878 x 10^10

Explanation:

since it is a combination = 38C17 = 2878 x 10^10

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Q:

A pizza can have 3 toppings out of possible 7 toppings.How many different pizza's can be made?

A) 49 B) 35
C) 27 D) 25
 
Answer & Explanation Answer: B) 35

Explanation:

There are 7 toppings in total,and by selecting 3,we will make different types of pizza.

 

This question is a combination since having a different order of toppings will not make a different pizza.

 

So,7C3 =35

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Q:

A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can't contain Nulls

A) TRUE B) FALSE
Answer & Explanation Answer: A) TRUE

Explanation:

Because a table can have only one primary key

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Q:

What is an Oracle index?

Answer

An index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

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Q:

What command would you use to create a backup control file?

Answer

Alter database backup control file to trace

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