Technology Questions

Q:

What is the difference between primary key & unique index ?

Answer

Primary key : a relational database constraint. Primary key consists of one or more columns that uniquely identify a row in the table. For a normalized relation, there is one designated primary key.


Unique index: a physical object that stores only unique values. There can be one or more unique indexes on a table.

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Q:

What is the difference between creating String as new() and literal ?

Answer

When we create string with new() Operator, it’s created in heap and not added into string pool while String created using literal are created in String pool itself which exists in PermGen area of heap.



String s = new String("Test");

does not put the object in String pool , we need to call String.intern() method which is used to put them into String pool explicitly. its only when you create String object as String literal e.g. String s = "Test" Java automatically put that into String pool.

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Q:

How can record locking be achieved in those DB2 versions which do not support it?

Answer

It can be done by setting the record length’s size to more than half of the page’s size.

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Q:

What is the syntax to inherit from a class in C#?

Answer

When a class is derived from another class, then the members of the base class become the members of the derived class. The access modifier used while accessing members of the base class specifies the access status of the base class members inside the derived class.

The syntax to inherit a class from another class in C# is as follows:
class MyNewClass : MyBaseclass

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Subject: .NET

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Q:

I do not want my class to be inherited by any other class. What should i do?

Answer You should declared your class as final. But you can't define your class as final, if it is an abstract class. A class declared as final can't be extended by any other class.
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Subject: Java

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Q:

What are the main advantages and disadvantages of Fiber-Optic-based networks?

Answer

Advantages      : More efficient and quality of service is better.


Dis advantages: Expensive, complicated

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Q:

What are the benefits of data integration?

Answer

Following are the benefits of data integration:


- Makes reporting, monitoring, placing customer information across the enterprise flexible and convenient.


- Data usage is efficient.


- Cost Effective.


- Risk adjusted profitability management as it allows accurate data extraction.


- Allows timely and reliable reporting, as data quality is the prime technology for business challenges.

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Q:

Define PL/SQL sequences and write syntax for a sequence

Answer

A sequence is a database object that is used to generate sequential number.


CREATE SEQUENCE seqname [increment] [minimum value][maximum value][start][cache][cycle]               Nextval and currval lets us get the next value and current value from the sequence.

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Subject: Oracle

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