Thursday, August 11, 2022

How To Prepare For Facebook Sql Interview

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What Is The Difference Between Delete And Truncate Statements

Hard SQL Interview Question From FACEBOOK | Data Science Coding Interviews (Popularity Percentage)

The TRUNCATE command is used to delete all the rows from the table and free the space containing the table.The DELETE command deletes only the rows from the table based on the condition given in the where clause or deletes all the rows from the table if no condition is specified. But it does not free the space containing the table.

Is Accenture Interview Hard

The Accenture interview might be a bit challenging, but can easily be cracked with proper preparations. Since Accenture is a high-performing company that wants to hire the best people possible, the different interview rounds at Accenture are challenging compared to regular interviews at large corporate companies. But the fact is that, with the perfect preparations, the interview can actually become relatively easy to succeed in the Accenture recruitment process.

Combining Outcomes From Tables

A candidate who is giving a SQL interview should be able to combine results from different tables by employing joins and set procedures.

When the interviewer wants you to demonstrate your knowledge of joins, you must excel in it. That alone will establish your practical expertise and suitability for the position.

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Q53 What Is The Difference Between Clustered And Non

The differences between the clustered and non clustered index in SQL are :

  • Clustered index is used for easy retrieval of data from the database and its faster whereas reading from non clustered index is relatively slower.
  • Clustered index alters the way records are stored in a database as it sorts out rows by the column which is set to be clustered index whereas in a non clustered index, it does not alter the way it was stored but it creates a separate object within a table which points back to the original table rows after searching.
  • One table can only have one clustered index whereas it can have many non clustered index.

  • Q9 What Is Cursor How To Use A Cursor

    Top sql queries interview questions and answers job interview tips

    After any variable declaration, DECLARE a cursor. A SELECT Statement must always be coupled with the cursor definition.

    To start the result set, move the cursor over it. Before obtaining rows from the result set, the OPEN statement must be executed.

    To retrieve and go to the next row in the result set, use the FETCH command.

    To disable the cursor, use the CLOSE command.

    Finally, use the DEALLOCATE command to remove the cursor definition and free up the resources connected with it.

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    Q4 What Is Rdbms How Is It Different From Dbms

    A relational database management system is a set of applications and features that allow IT professionals and others to develop, edit, administer, and interact with relational databases. Most commercial relational database management systems use Structured Query Language to access the database, which is stored in the form of tables. The RDBMS is the most widely used database system in businesses all over the world. It offers a stable means of storing and retrieving massive amounts of data.

    Databases, in general, hold collections of data that may be accessed and used in other applications. The development, administration, and use of database platforms are all supported by a database management system.

    A relational database management system is a type of database management system that stores data in a row-based table structure that links related data components. An RDBMS contains functions that ensure the datas security, accuracy, integrity, and consistency. This is not the same as the file storage utilized by a database management system.

    The following are some further distinctions between database management systems and relational database management systems:

    What Are The Differences Between Oltp And Olap

    OLTP stands for Online Transaction Processing, is a class of software applications capable of supporting transaction-oriented programs. An important attribute of an OLTP system is its ability to maintain concurrency. OLTP systems often follow a decentralized architecture to avoid single points of failure. These systems are generally designed for a large audience of end-users who conduct short transactions. Queries involved in such databases are generally simple, need fast response times, and return relatively few records. A number of transactions per second acts as an effective measure for such systems.

    OLAP stands for Online Analytical Processing, a class of software programs that are characterized by the relatively low frequency of online transactions. Queries are often too complex and involve a bunch of aggregations. For OLAP systems, the effectiveness measure relies highly on response time. Such systems are widely used for data mining or maintaining aggregated, historical data, usually in multi-dimensional schemas.

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    Tips To Crack Sql Interview Questions

    Follow these proven tips to answer and nail SQL interview questions:

    1. Ask Questions

    When the interviewer asks a question, take some time to understand the questions completely and ask clarifying questions if necessary. Know the datatypes of the columns present, if there are any primary keys etc.

    2. Identify the Relevant Columns

    You donât require all the columns present in the table for your output. Identify the columns you need to work on, so you can concentrate on those.

    3. Think About What Your Final Answer Should Look Like

    While trying to solve the problem, keep the answer in your mind. Imagine what your final output should look like. This helps you to clear your mind and think about the logical ways to solve the problem.

    4. Solve the Query One Step at a Time

    Break down the problem into subparts and solve them one step at a time. If you have subqueries, start by solving the subquery first and then think about the main query. It helps you to concentrate on bits of the problem rather than the problem as a whole.

    5. Include Comments

    Include comments to explain what each step of your query performs. It helps you and the interviewer to understand the code and enables you to keep track of where you are.

    6. Use Formatting

    7. Talk Through the Process

    Itâs important to explain to the interviewer what youâre doing. It helps them understand how you approach a problem and give some tips if youâre stuck anywhere. So, make sure to explain what, why, and how of each step.

    Q3 What Do You Mean By Dbms What Are Its Different Types

    Solving a SQL Interview Question by FACEBOOK | (Data Science Interview) SMS Confirmations From Users

    A Database Management System is a software application that interacts with the user, applications, and the database itself to capture and analyze data. A database is a structured collection of data.

    A DBMS allows a user to interact with the database. The data stored in the database can be modified, retrieved and deleted and can be of any type like strings, numbers, images, etc.

    There are two types of DBMS:

    • Relational Database Management System: The data is stored in relations . Example MySQL.
    • Non-Relational Database Management System: There is no concept of relations, tuples and attributes. Example MongoDB

    Lets move to the next question in this SQL Interview Questions.

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    Q27 What Is Cursor How To Use A Cursor

    After any variable declaration, DECLARE a cursor. A SELECT Statement must always be coupled with the cursor definition.

    To start the result set, move the cursor over it. Before obtaining rows from the result set, the OPEN statement must be executed.

    To retrieve and go to the next row in the result set, use the FETCH command.

    To disable the cursor, use the CLOSE command.

    Finally, use the DEALLOCATE command to remove the cursor definition and free up the resources connected with it.

    How Can We Start Restart And Stop The Postgresql Server

    • To start the PostgreSQL server, we run:
    service postgresql start
    • Once the server is successfully started, we get the below message:
    Starting PostgreSQL: ok
    • To restart the PostgreSQL server, we run:
    service postgresql restart

    Once the server is successfully restarted, we get the message:

    Restarting PostgreSQL: server stoppedok
    • To stop the server, we run the command:
    service postgresql stop

    Which statement is true for a PRIMARY KEY constraint?

    Which statement is false for a FOREIGN KEY constraint?

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    How To Nail Your Next Tech Interview

    SQL interview questions are a critical piece of technical interviews and coding interviews. Most engineering roles, such as software engineer, data scientist, and data engineer, require SQL as a secondary skill. So, when youâre preparing for technical interviews, it is a good practice to prepare basic SQL questions. Some companies conduct separate SQL interview rounds for roles like data engineer and data scientist.

    If you are a software engineer, software developer, engineering manager, or tech lead preparing for a tech interview, check out our technical interview checklist, interview questions page, and salary negotiation e-book to get interview-ready!

    Having trained over 9,000 software engineers, we know what it takes to crack the toughest tech interviews. Since 2014, Interview Kickstart alums have been landing lucrative offers from FAANG and Tier-1 tech companies, with an average salary hike of 49%. The highest ever offer received by an IK alum is a whopping $933,000!

    At IK, you get the unique opportunity to learn from expert instructors who are hiring managers and tech leads at Google, Facebook, Apple, and other top Silicon Valley tech companies.

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    To help you with your SQL interview preparation, weâve gathered some frequently asked SQL interview questions. Hereâs what weâll discuss in this article:

    Solution Of Sql Interview Question #3

    Common Entry Level SQL Developer Interview Questions

    Solution:

    SELECT department_name, AVG AS avg_salariesFROM employeesJOIN salariesON employees.employee_id = salaries.employee_idGROUP BY department_nameHAVING AVG <  500 

    Note: You can solve this task using a subquery, too but in an interview situation the interviewer will like the above solution better.

    Brief explanation:

    1. First JOIN the two tables:

    SELECT *FROM employeesJOIN salariesON employees.employee_id = salaries.employee_id

    Watch out! Use the employee_id column not the employee_name.

    2. Then use the AVG function with a GROUP BY clause and replace the * with the appropriate columns.

    3. And the last step is to use a HAVING clause to filter by the result of the AVG function. function.)Watch out: in the HAVING line, you cant refer to the alias you have to use the whole function itself again!

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    Solution Of Sql Interview Question #1

    The solution code is:

    SELECT authors.author_name, SUM AS sold_sumFROM authorsJOIN booksON books.book_name = authors.book_nameGROUP BY authors.author_nameORDER BY sold_sum DESCLIMIT 3 

    And here is a short explanation:

    1. First you have to initiate the JOIN. I joined the two tables by using:

    SELECT *FROM authorsJOIN booksON books.book_name = authors.book_name 

    2. After that, I used a SUM function with a GROUP BY clause. This means that in the SELECT statement I had to replace the * with the author_name and sold_copies columns.

    3. Eventually, I ORDERed the results in DESCending order.

    How Do I Prepare For Accenture Interview

    Following are the few points that you can take care of while preparing for the Accenture interview:

    • Do your homework: Mainly Understand the job role for which you are applying and also learn a few company-related information about Accenture. Research on these things in advance, whether that is exploring the Accentures company website or discussing with a friend who works in Accenture.
    • Think through your answers: While the Accenture interview topics can range from different technical aspects and personal skills, prepare in advance as to how you can answer the questions. Think about the requirements of the role, your accomplishments, and your personal aspirations, which essentially helps you in preparing for the interview conversations.
    • Have questions ready: Most of the time, your interviewer will give you time for asking questions. So it is important to have a question ready to ask! Not one that has already been answered, but one that demonstrates your insightfulness & interest in the position and also about the company. For more tips check the above section.

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    Questions About A Query

    This second category of question gives you an SQL query and asks you a question about it. This tests your ability to read, interpret, analyze, and debug code written by others.

    Forms query analysis questions may take:

    Given a query,

  • Put the clauses in order by how SQL would run them.

  • Identify the error and correct it.

  • Predict what the query will return.

  • Explain what problem the query is meant to solve.

  • What Are Aggregate And Scalar Functions

    Advanced Facebook Data Science SQL interview question [RANK()]

    An aggregate function performs operations on a collection of values to return a single scalar value. Aggregate functions are often used with the GROUP BY and HAVING clauses of the SELECT statement. Following are the widely used SQL aggregate functions:

    • AVG – Calculates the mean of a collection of values.
    • COUNT – Counts the total number of records in a specific table or view.
    • MIN – Calculates the minimum of a collection of values.
    • MAX – Calculates the maximum of a collection of values.
    • SUM – Calculates the sum of a collection of values.
    • FIRST – Fetches the first element in a collection of values.
    • LAST – Fetches the last element in a collection of values.

    Note: All aggregate functions described above ignore NULL values except for the COUNT function.

    A scalar function returns a single value based on the input value. Following are the widely used SQL scalar functions:

    • LEN – Calculates the total length of the given field .
    • UCASE – Converts a collection of string values to uppercase characters.
    • LCASE – Converts a collection of string values to lowercase characters.
    • MID – Extracts substrings from a collection of string values in a table.
    • CONCAT – Concatenates two or more strings.
    • RAND – Generates a random collection of numbers of a given length.
    • ROUND – Calculates the round-off integer value for a numeric field .
    • NOW – Returns the current date & time.
    • FORMAT – Sets the format to display a collection of values.

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    Why Is Sql So Popular

    SQL stands for Structured Query Language, a domain-specific language for managing data in the Database Management System . Database Management System is a software that handles the creation, updation, and management of data.

    SQL is one of the most desired skills in the market, as there is a massive usage of DBMS in every software. Every application or software you develop has some data associated with it and needs the DBMS principles to manage it.

    Q14 How To Create Empty Tables With The Same Structure As Another Table

    To create empty tables: Using the INTO operator to fetch the records of one table into a new table while setting a WHERE clause to false for all entries, it is possible to create empty tables with the same structure. As a result, SQL creates a new table with a duplicate structure to accept the fetched entries, but nothing is stored into the new table since the WHERE clause is active.

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    Are You Ready To Nail Your Next Tech Interview

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    How Long Is The Interview Process At Accenture

    The Ultimate Guide to SQL Interview Questions

    On average, the Accenture interview process will usually go around one month from beginning to end, although it might take longer during busy recruitment periods. Once the online application and interviews of a particular candidate are completed, Accenture normally aims to respond to their decision within 1015 working days. So if you have cleared an assessment test, you should be receiving positive feedback within 2 weeks from its conclusion.

    Accenture receives a large number of applications for different roles every year. So there is a higher chance that it can close the applications earlier than expected, so be sure to apply early.

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    Q20 What Is The Difference Between The Rank And Dense: Rank Functions

    The RANK function in the result set defines the rank of each row within your ordered partition. If both rows have the same rank, the next number in the ranking will be the previous rank plus a number of duplicates. If we have three records at rank 4, for example, the next level indicated is 7.

    The DENSE_RANK function assigns a distinct rank to each row within a partition based on the provided column value, with no gaps. It always indicates a ranking in order of precedence. This function will assign the same rank to the two rows if they have the same rank, with the next rank being the next consecutive number. If we have three records at rank 4, for example, the next level indicated is 5.

    Q21. What are Tables and Fields?

    A table is a collection of data components organized in rows and columns in a relational database. A table can also be thought of as a useful representation of relationships. The most basic form of data storage is the table. An example of an Employee table is shown below.

    ID
    30000

    A Record or Row is a single entry in a table. In a table, a record represents a collection of connected data. The Employee table, for example, has four records.

    A table is made up of numerous records , each of which can be split down into smaller units called Fields. ID, Name, Department, and Salary are the four fields in the Employee table above.

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