Technology Questions

Oracle constraints are used to maintain consistent of data and ensure the data is properly maintained. A constraint is more or less a restriction we try to apply on a table.
Types of constraints:
- Check constraints
- NOT NULL constraint
- PRIMARY KEY constraint
- REFERENCES constraint
- UNIQUE constraint

Dropped tables can be recovered using DROP TABLE flashback. It works the way recycle bin works.
Example:
FLASHBACK TABLE EMPLOYEE TO BEFORE DROP;
The most recently dropped table with that original name is retrieved from the recycle bin, with its original name.

PL/SQL exceptions are raised using the RAISE command. This command is used when exceptions are defined by programmer and not implicit exceptions.

Example:

Declare and raising an exception:

DECLARE

short_of_attendance EXCEPTION;

min_attendance NUMBER(4);

BEGIN

...

IF min_attendance < 10 THEN

RAISE short_of_attendance;

END IF;

EXCEPTION

WHEN short_of_attendance THEN

-- handle the error

END;

The standard query operators in LINQ are the extension methods that form the LINQ pattern. These operators form an API that enables querying of any .NET array or collection. It operates on sequences and allows you to perform operations, such as determining if a value exists in the sequence and performing an aggregated function, such as a summation over a sequence.

Internet Service Provider (ISP) is a company offering access to internet. They offer various services:

1. Internet Access

2. Domain name registration

3. Dial-up access

4. Leased line access

There exist several ways to connect to the internet. Following are these connection types available:

* Dial-up Connection

* ISDN

* DSL

* Cable TV Internet connections

* Satellite Internet connections

* Wireless Internet Connections

1.Main difference is methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can have instance methods that implements a default behavior.

2.Variables declared in a Java interface is by default final. An abstract class may contain non-final variables.

3.Members of a Java interface are public by default. A Java abstract class can have the usual flavors of class members like private, protected, etc..

4.Java interface should be implemented using keyword “implements”; A Java abstract class should be extended using keyword “extends”.

5.An interface can extend another Java interface only, an abstract class can extend another Java class and implement multiple Java interfaces.

6.A Java class can implement multiple interfaces but it can extend only one abstract class.

7.Interface is absolutely abstract and cannot be instantiated; A Java abstract class also cannot be instantiated, but can be invoked if a main() exists.

8.In comparison with java abstract classes, java interfaces are slow as it requires extra indirection.

READNEXT reads the next record from a browse operation for any of the three VSAM files.