Virtual Galaxy Infotech Interview Questions and Answers

A subquery is a query nested inside another query. It is used to retrieve data from multiple tables or perform complex calculations.

• A subquery is enclosed within parentheses and is usually placed within the WHERE or HAVING clause of the outer query.

• The result of the subquery is used by the outer query to filter or manipulate the data.

• Subqueries can be used to retrieve data from multiple tables, perform calculations, or...read more

Delete and Truncate are SQL commands used to remove data from a table, but they differ in their approach.

• DELETE is a DML command that removes specific rows from a table based on a condition.

• TRUNCATE is a DDL command that removes all the rows from a table and resets the identity of the table.

• DELETE is slower than TRUNCATE as it logs the data changes, whereas TRUNCATE does not.

• DELETE can be rolled back, but TRUNCATE cann...read more

A View is a user interface element that displays information or interacts with the user.

• A View is a fundamental building block of Android UI.

• It can be a button, text field, image, or any other interactive element.

• Views can be arranged in a hierarchy to create complex UI layouts.

• Each View has its own set of properties that can be customized, such as size, color, and behavior.

Sample queries for PROCEDURE, FUNCTION, CURSOR

• PROCEDURE: CREATE PROCEDURE get_employee_details AS SELECT * FROM employees;

• FUNCTION: CREATE FUNCTION get_employee_count RETURN NUMBER IS count NUMBER; BEGIN SELECT COUNT(*) INTO count FROM employees; RETURN count; END;

• CURSOR: DECLARE emp_cursor CURSOR FOR SELECT * FROM employees; OPEN emp_cursor; FETCH emp_cursor INTO emp_record; CLOSE emp_cursor;

There are three types of loops: for, while, and do-while.

• For loop: executes a block of code a fixed number of times.

• While loop: executes a block of code as long as the condition is true.

• Do-while loop: executes a block of code at least once, then repeats as long as the condition is true.

Packages, Index, and Sequences are all related to data organization and management in programming.

• Packages are collections of related classes and interfaces that are used to organize code.

• Index is a data structure that allows for efficient searching and retrieval of data.

• Sequences are ordered collections of elements that can be accessed by their position in the sequence.

• Examples include the Java Collections Framework, ...read more

Procedures do not return values while functions return values.

• Procedures are used to perform an action while functions are used to calculate and return a value.

• Functions can be used in expressions while procedures cannot.

• Functions have a return type while procedures do not.

• Functions can have input parameters and return values while procedures can only have input parameters.

• Examples of functions include Math.max() and S...read more

Canvas in forms can be of different types like HTML5 Canvas, SVG Canvas, and PDF Canvas.

• HTML5 Canvas allows for drawing graphics using JavaScript

• SVG Canvas is scalable and can be manipulated with CSS

• PDF Canvas is used for generating PDF documents programmatically

There are various types of forms used in software development.

• Web Forms - used for collecting user input on a website

• Windows Forms - used for creating desktop applications

• Mobile Forms - used for creating mobile applications

• Dialog Forms - used for displaying messages or alerts to the user

• Modal Forms - used for capturing user input before allowing further interaction

• Wizard Forms - used for guiding the user through a mult...read more

Triggers used in forms and their levels and uses.

• Types of triggers: Pre-Form, Post-Form, Item, Validation, Navigation, Transaction

• Pre-Form triggers execute before the form is displayed

• Post-Form triggers execute after the form is closed

• Item triggers execute when a user interacts with an item on the form

• Validation triggers execute when a user enters data into an item

• Navigation triggers execute when a user navigates betwe...read more

Single row functions operate on a single row and return one result per row. Group functions operate on a group of rows and return one result per group.

• Single row functions include: numeric functions, character functions, date functions, conversion functions, and general functions.

• Group functions include: AVG, COUNT, MAX, MIN, SUM.

• Single row functions can be used in SELECT, WHERE, and ORDER BY clauses.

• Group functions ar...read more

Set operators are used to combine or compare sets in SQL.

• UNION operator combines two sets and removes duplicates

• INTERSECT operator returns only common elements in two sets

• EXCEPT operator returns elements in one set but not in the other

• ALL keyword can be used with set operators to include duplicates

• Set operators can only be used with compatible data types

Yes, exception handling is necessary in queries.

• Exception handling helps to handle unexpected errors and prevent application crashes.

• It also helps to provide meaningful error messages to the user.

• In SQL, exceptions can be handled using the TRY-CATCH block.

• In NoSQL databases, exceptions can be handled using error codes and messages.

Master table should have a primary key which is used as a foreign key in the transaction table.

• Create a primary key in the master table

• Create a foreign key in the transaction table that references the primary key in the master table

• Use the foreign key to link the two tables on forms

Reports can be categorized into operational, analytical, and statutory reports.

• Operational reports provide information on day-to-day activities.

• Analytical reports provide insights into data trends and patterns.

• Statutory reports are required by law and must be submitted to regulatory bodies.

• Other types of reports include ad hoc reports, exception reports, and dashboards.

Constraints are rules enforced on data in a table, while triggers are actions performed in response to certain events.

• Constraints ensure data integrity and consistency, while triggers automate actions based on specific events.

• Constraints are defined at the time of table creation, while triggers are created separately.

• Constraints can be used to enforce rules such as unique values, primary keys, and foreign keys, while t...read more