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

- A web page with large number of images takes a longer time to load. This is because each image separately sends out a http request.

- The concept of CSS sprite helps in reducing this loading time for a web page by combining various small images into one image. This reduces the numbers of http request and hence the loading time.

In general, a Nine-patch image allows resizing that can be used as background or other image size requirements for the target device. The Nine-patch refers to the way you can resize the image: 4 corners that are unscaled, 4 edges that are scaled in 1 axis, and the middle one that can be scaled into both axes.

When ever two or more threads are sharing same data for updating then unpredicted result will be there in the data.

For Example take a thread is depositing amount in Account Object and another thread is withdrawing amount from the same Account Object.

when ever both threads are executed simultaneously then unexpected result is stored in the balance of the  Account Object. 

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.

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

An index is a object which is used to improve performance during retrieval of records.

CREATE [UNIQUE] INDEX index_name 

ON employee[emp_id, emp_name,dept_id]

[COMPUTE STATISTICS]

The UNIQUE keyword is used when combined values of the index should be unique.

The COMPUTE STATISTICS during the creation of index optimizes the plan of execution of the SQL statement and improves performance.

Outside the package if any other class other than JVM calls the finalize method our class then it is not allowed