Mphasis Interview Questions, Process, and Tips

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column.

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;

Some built-in functions in SQL include AVG, COUNT, MAX, MIN, SUM, and CONCAT.

• AVG: Calculates the average value of a numeric column

• COUNT: Counts the number of rows in a result set

• MAX: Returns the maximum value in a column

• MIN: Returns the minimum value in a column

• SUM: Calculates the sum of values in a column

• CONCAT: Concatenates two or more strings together

Types of cursors in database management systems include implicit, explicit, and parameterized cursors.

• Implicit cursors are automatically created by the database when a SQL statement is executed.

• Explicit cursors are defined by the programmer and give more control over the result set.

• Parameterized cursors allow for dynamic SQL statements with parameters.

• Examples: SELECT statement using implicit cursor, DECLARE, OPEN, FET...read more

Procedures are used to perform an action, while functions return a value.

• Procedures do not return a value, while functions do.

• Functions can be used in SQL queries, while procedures cannot.

• Functions can be called from within SQL statements, while procedures cannot.

• Procedures can have OUT parameters to return multiple values, while functions can only return a single value.

Use a subquery to find the third highest salary in a table.

• Use the RANK() function to assign a rank to each salary in descending order.

• Filter the results to only include rows with a rank of 3.

• Consider handling ties in salaries appropriately.

A package is a collection of related procedures, functions, variables, and other PL/SQL constructs.

• Packages help organize and encapsulate code for easier maintenance and reuse.

• They can contain both public and private elements.

• Packages can be used to group related functionality together, improving code modularity.

• Example: CREATE PACKAGE my_package AS ... END my_package;

Resolved a critical bug causing data loss and implemented a new feature for better user experience.

• Identified root cause of data loss bug by analyzing database queries and logs

• Collaborated with cross-functional teams to prioritize and implement a fix

• Designed and implemented a new feature based on user feedback to enhance usability

Different types of indexes include B-tree, Bitmap, Function-based, and Reverse key indexes.

• B-tree indexes are the most common type and are suitable for most indexing needs.

• Bitmap indexes are used for columns with low cardinality, such as gender or status columns.

• Function-based indexes are created based on expressions or functions applied to columns.

• Reverse key indexes store keys in reverse order to reduce contention in

Analytical functions in SQL are used to perform calculations across a set of rows related to the current row.

• Analytical functions operate on a group of rows and return a single result for each row.

• They can be used to calculate running totals, moving averages, rank, percentiles, etc.

• Examples include ROW_NUMBER(), RANK(), DENSE_RANK(), SUM() OVER(), AVG() OVER().

Aggregate functions in SQL are functions that operate on a set of values and return a single value as output.

• Aggregate functions include functions like SUM, AVG, COUNT, MIN, and MAX.

• They are used with the GROUP BY clause to perform calculations on groups of rows.

• Examples: SELECT SUM(salary) FROM employees; SELECT AVG(age) FROM students GROUP BY class;

I identified and optimized slow-performing SQL queries by analyzing execution plans and indexing strategies.

• Identified slow-performing SQL queries using tools like Oracle SQL Developer or TOAD.

• Analyzed execution plans to understand query performance bottlenecks.

• Optimized queries by rewriting SQL code, adding indexes, or restructuring data.

• Used tools like Explain Plan or SQL Tuning Advisor to improve query performance.

• R...read more

Data modeling is the process of creating a visual representation of data structures and relationships within a database.

• Data modeling helps in organizing and understanding complex data systems.

• It involves identifying entities, attributes, and relationships between them.

• Examples include ER diagrams, UML diagrams, and relational data models.

I conducted thorough analysis by reviewing code, logs, and discussing with team members.

• Reviewed code to identify potential issues

• Analyzed logs for error messages and patterns

• Discussed with team members to gather insights and perspectives

• Used debugging tools to trace the root cause

A trigger in database management is a special type of stored procedure that is automatically executed when certain events occur in a database.

• Triggers can be used to enforce business rules, maintain referential integrity, and automate repetitive tasks.

• There are two main types of triggers: row-level triggers and statement-level triggers.

• Row-level triggers are fired for each row affected by a triggering statement, while ...read more

Cucumber is a testing framework that supports Behavior Driven Development (BDD) using plain language for writing test cases.

• Cucumber allows writing test cases in Gherkin language, which is human-readable.

• It promotes collaboration between developers, testers, and non-technical stakeholders.

• Example of a Gherkin scenario: 'Given the user is on the login page, When they enter valid credentials, Then they should be redirect...read more

Interfaces define contracts for classes, while abstraction hides implementation details, focusing on essential features.

• An interface can contain method signatures but no implementation, e.g., 'public interface Animal { void makeSound(); }'

• Abstraction can be achieved using abstract classes, which can have both abstract methods and concrete methods, e.g., 'abstract class Shape { abstract void draw(); }'

• A class can implem...read more

In Java, exceptions are handled using try-catch blocks, allowing graceful error management and maintaining program flow.

• Use try-catch blocks to catch exceptions: try { // code that may throw an exception } catch (ExceptionType e) { // handle exception }

• Use finally block for cleanup: try { // code } catch (Exception e) { // handle exception } finally { // cleanup code }

• Throw exceptions using '...read more

Enhancing Angular app performance involves optimization techniques like lazy loading, change detection strategies, and efficient data handling.

• Use Lazy Loading: Load feature modules only when needed to reduce initial load time. Example: Implementing lazy loading in the routing module.

• Optimize Change Detection: Use OnPush strategy to limit checks to only when inputs change. Example: Using ChangeDetectionStrategy.OnPush ...read more

Data binding in Angular connects component data to the template, enabling dynamic updates and interaction.

• 1. **Interpolation**: Use double curly braces to bind component properties to the template. Example: `{{ title }}`.

• 2. **Property Binding**: Bind DOM properties to component properties using square brackets. Example: `<img [src]='imageUrl'>`.

• 3. **Event Binding**: Use parentheses to listen to events and call co...read more

Angular lifecycle events manage component states from creation to destruction, enabling developers to hook into key moments.

• ngOnInit: Called once after the first ngOnChanges. Ideal for initialization logic. Example: Fetching data from a service.

• ngOnChanges: Invoked before ngOnInit and whenever one or more data-bound input properties change. Example: Reacting to input changes.

• ngDoCheck: Called during every change detect...read more

Angular handles events using event binding, directives, and services for user interactions and component communication.

• Event Binding: Use parentheses to bind events in templates, e.g., <button (click)='onClick()'>Click Me</button>.

• Event Object: Access event properties by passing $event, e.g., <input (input)='onInput($event)'>.

• Custom Events: Use EventEmitter to create and emit custom events from child ...read more

Follow best practices in Angular to enhance code quality, maintainability, and performance.

• Use Angular CLI for project setup and management to ensure consistency.

• Organize code into modules for better separation of concerns.

• Implement lazy loading for feature modules to improve application performance.

• Utilize services for data management and business logic, keeping components lean.

• Follow the Angular style guide for namin...read more

Dependency injection in Angular is a design pattern that allows a class to receive its dependencies from external sources rather than creating them itself.

• Promotes code reusability and modularity by decoupling components.

• Angular's injector is responsible for creating and managing dependencies.

• Services can be injected into components, directives, and other services.

• Example: A logging service can be injected into multipl...read more

ngShow toggles visibility with CSS, while ngIf adds/removes elements from the DOM based on a condition.

• ngShow: Uses CSS display property to show/hide elements without removing them from the DOM.

• Example: <div ng-show='isVisible'>Content</div> - Content remains in DOM but hidden if isVisible is false.

• ngIf: Conditionally includes or excludes elements from the DOM based on the expression's truthiness.

• Example: &...read more

call, apply, and bind are methods to set the context of 'this' in JavaScript functions.

• call: Invokes a function with a specified 'this' value and arguments provided individually. Example: func.call(obj, arg1, arg2);

• apply: Similar to call, but arguments are provided as an array. Example: func.apply(obj, [arg1, arg2]);

• bind: Returns a new function with a specified 'this' value, allowing for later invocation. Example: cons

Map, filter, and reduce are array methods in JavaScript for transforming and processing data.

• Map: Creates a new array by applying a function to each element. Example: [1, 2, 3].map(x => x * 2) results in [2, 4, 6].

• Filter: Creates a new array with elements that pass a test. Example: [1, 2, 3].filter(x => x > 1) results in [2, 3].

• Reduce: Reduces an array to a single value by applying a function. Example: [1, 2, ...read more

Different looping constructs in programming serve unique purposes for iterating over collections.

• for: A traditional loop that iterates over a range of numbers. Example: for (let i = 0; i < 5; i++) { console.log(i); }

• for each: A method to iterate over elements in an array or collection. Example: array.forEach(item => console.log(item));

• for of: A modern loop for iterating over iterable objects like arrays, strings,...read more