What Do You Know About Sql
Recruiters arent asking for an exhaustive list of every SQL topic that youre familiar with. Rather, theyre trying to discern whether you have a general understanding of the field, and whether you have the practical experience to boot.
Start with a general overview of what SQL is, and how its used in business contexts. Then, detail some of your learning journey, whether thats been in college or an online course that covers SQL. Finally, tell them about your relevant projects and how you employed theoretical foundations.
What Is The Difference Between A Where Clause And A Having Clause In Sql
Answer all of the given differences when this data analyst interview question is asked, and also give out the syntax for each to prove your thorough knowledge to the interviewer.
|WHERE clause operates on row data.
|The HAVING clause operates on aggregated data.
|In the WHERE clause, the filter occurs before any groupings are made.
HAVING is used to filter values from a group.
|Aggregate functions cannot be used.
|Aggregate functions can be used.
Syntax of WHERE clause:
ORDER BY column_name
How Long Does It Take To Learn Data Analysis
The time taken to learn data analytics varies from person to person. It depends on your dedication to studying, prior knowledge of the field, and work experience in data analytics. While some of the concepts may take a few days, others may take a couple of months to grasp. When you take our online Data Analytics certification program, you should apply the concepts you learned to real-world use cases to gain practical exposure and reinforce your learning.
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Explain The Difference Between Oltp And Olap
OLTP: It stands for online transaction processing, and we can consider it to be a category of software applications that are efficient for supporting transaction-oriented programs. One of the important attributes of the OLTP system is its potential to keep up the consistency. The OLTP system often follows decentralized planning to keep away from single points of failure. This system is generally designed for a large audience of end users to perform short transactions. The queries involved in such databases are generally simple, need fast response time, and, in comparison, return in only a few records. So, the number of transactions per second acts as an effective measure for those systems.
OLAP: It stands for online analytical processing, and it is a category of software programs that are identified by a comparatively lower frequency of online transactions. For OLAP systems, the efficiency of computing depends highly on the response time. Hence, such systems are generally used for data mining or maintaining aggregated historical data, and they are usually used in multidimensional schemas.
The Sql Interview Questions Asked By The Faang Companies
FAANG is an acronym for the five most famous tech companies: Facebook, Amazon, Apple, Netflix, and Google. Why would you specially prepare for the questions asked by those companies, except being in awe of the possibility of working for them? They might seem or even be attractive, but that is not the main reason why you would pay special attention if you want to work at those companies.The main reason is their SQL interview questions are a bit different. As tech companies, their business heavily relies on data. And where there is data, there is SQL which the FAANG companies often use. Hence they want to be absolutely certain that their employees know SQL in depth. You will always get SQL interview questions with a little twist. The twist being their questions are more practical and concerning a case study with real problems and data a certain company is facing in their everyday business. These are arguably the next level of the Open Ended SQL Interview Questions that we saw earlier.
Have a look at this example from Google:
Question #9: Activity Rank
“Find the email activity rank for each user. Email activity rank is defined by the total number of emails sent. The user with the highest number of emails sent will have a rank of 1, and so on. Output the user, total emails, and their activity rank. Order records by the total emails in descending order. Sort users with the same number of emails in alphabetical order.
Question #10: Find the nominee who has won the most Oscars
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Highest Salary By Department
Lets discuss salaries some more. This time, were interested in obtaining the highest salaries by department. To make things interesting, weve decided to split the data into two tables department and employee_detail.
Heres the code to create and populate both tables:
The table department is sort of a lookup table, and has only two rows:
Image 10 Table department
The employee_detail table holds a reference to the department table:
Image 11 Table employee detail
To get the highest salary by department, well have to join both tables and use the IN clause to keep only the highest salary by department:
Heres the result set:
Image 12 Highest salary by department
Get comfortable with writing joins, as all companies structure their databases by respecting the normal forms, which means each entity type is stored in a dedicated table to reduce redundancy.
Explain The Cases To Use Having Versus Where
SQL offers HAVING clauses to filter a group of data in a database.
For example, company XYZ has a list of employees who have more than 1 year of experience.
The database contains rows and columns including the employee name, joining data, experience, and experience level.
You can retrieve a list of employees who have more than 5 years of experience.
The HAVING clause provides you with a way to control the information and modify the data with a bunch of data.
The syntax of the HAVING clause is the HAVING condition.
In the example, we can retrieve the list of employees having more than 5 years of experience by querying the database as below:
SELECT employee_name, exp_level,FROM EMPLOYEEGROUP BY experienceHAVING COUNT > 5
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What Is The Difference Between Drop And Truncate Statements
If a table is dropped, all things associated with the tables are dropped as well. This includes – the relationships defined on the table with other tables, the integrity checks and constraints, access privileges and other grants that the table has. To create and use the table again in its original form, all these relations, checks, constraints, privileges and relationships need to be redefined. However, if a table is truncated, none of the above problems exist and the table retains its original structure.
What Is A Schema In Sql
A schema is a logical representation of the different objects in the database. Think of it as a mapping of all the tables, functions, stored procedures, and indexes that are part of a database. Creating schemas allows you to give different users different levels of access and easily share the logical structure of the database with multiple users. Read more about schema in SQL here.
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Why Should I Learn Sql Developer From Intellipaat
Intellipaats SQL Developer training will make you fully proficient in this programming language, relational database concepts, techniques of querying, creating subqueries, joins, and unions, indexing, optimization theory, installing SQL Server, clustering, etc. The SQL certification online course content is in line with the requirements for clearing the SQL Server certification exam.
You will be working on real-time projects and step-by-step assignments that have high relevance in the corporate world, and the course curriculum is designed by industry experts. Upon the completion of the course, you can apply for some of the best jobs in top MNCs around the world at top salaries. Intellipaat offers lifetime access to videos, materials, 24/7 support, and material upgrading to the latest version at no extra fee. Hence, it is clearly a one-time investment to sign up for this online SQL training and certification.
How To Ace Your Sql Interview
The best way to ace an interview is to prepare, prepare, prepare. This is especially true for the SQL interview, where so much of it focuses on technical knowledge that cannot be attained any way else but through consistent practice and familiarity.
With whiteboard tests, it helps to replicate the interview environment by purchasing your own whiteboard to practice on. Ask a friend to roleplay as the interviewer so you can get comfortable writing code without being allowed to use technological aids like Github CoPilot or searching StackOverflow for answers, all in front of an audience.
Brush up on your SQL syntax by practicing on as many questions as you can. Live coding questions are especially tough as not many are used to being watched while coding. To help with the nerves, its critical to get exposure to as many types of SQL questions as possible. These questions vary greatly in complexity and can be tricky to prepare for. Many aspiring programmers turn to online programming question banks like LeetCode and HackerRank, which have a wide range of SQL coding challenges.
Other users often post their solutions online, and reverse-engineering better solutions is a great teaching tool as well. The great thing about practicing on these well-regarded platforms is that many companies draw their questions from there, so youll likely come across questions that you have worked on previously.
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Q3 What Do You Mean By Dbms What Are Its Different Types
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.
What Is The Difference Between Drop And Truncate Commands
If a table is dropped, all things associated with that table are dropped as well. This includes the relationships defined on the table with other tables, access privileges, and grants that the table has, as well as the integrity checks and constraints.
To create and use the table again in its original form, all the elements associated with the table need to be redefined.
However, if a table is truncated, there are no such problems as mentioned above. The table retains its original structure.
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Q25 What Are Some Common Clauses Used With Select Query In Sql
The following are some frequent SQL clauses used in conjunction with a SELECT query:
WHERE clause: In SQL, the WHERE clause is used to filter records that are required depending on certain criteria. ORDER BY clause: The ORDER BY clause in SQL is used to sort data in ascending or descending order depending on specified field . GROUP BY clause: GROUP BY clause in SQL is used to group entries with identical data and may be used with aggregation methods to obtain summarised database results. HAVING clause in SQL is used to filter records in combination with the GROUP BY clause. It is different from WHERE, since the WHERE clause cannot filter aggregated records.
What Is An Sql View
A View is a virtual table that has contents obtained as a result of an SQL query. You can save the results of a complex SQL query to a view. Views are typically created with the CREATE OR REPLACE VIEW view_name statement, but the syntax may vary from one DBMS to the other.
For example, lets imagine you want to create a view that contains only sales where the total amount was greater than or equal to USD 50 . The resulting view v_sales_gte_50 and the base table would look like this:
Image 3 SQL View demonstration
And the underlying SQL query would look something like this:
SQL Views are used when you want to save time by reducing the amount of SQL you need to write, and when you dont want to allow each user to see every part of the database.
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How Can You Create Empty Tables With The Same Structure As Another Table
This can be achieved by fetching the records of one table into a new table using the INTO operator while fixing a WHERE clause to be false for all records. In this way, SQL prepares the new table with a duplicate structure to accept the fetched records. However, there are no records that will get fetched due to the WHERE clause in action. Therefore, nothing is inserted into the new table, thus creating an empty table.
SELECT * INTO Students_copyFROM Students WHERE 1 = 2
Microsoft Data Scientist Sql Interview Question
Employee Project Budgets
Find the top five most expensive projects by the amount of budget allocated to each employee on the project. Exclude projects with 0 employees. Assume each employee works on only one project. The output should be the project title and the budget thats allocated to each employee . Display the top 5 projects with the highest budget-to-employee ratio first.
**Please note that this question has since been updated on the StrataScratch platform, available here. In this article and video, we discuss a different version of the question.
Taking clues from the question above, the following initial assumptions are made:
Our dataset provides the following breakdown:
- id individual id of each project
- title name of the project
- budget total cost of each project
- emp_id integer value of the employees id
- project_id unique id for each project, same value as id in ms_projects table
Upon reviewing the budget column in ms_projects, one can see that we are working with whole numbers, therefore the assumption that we are working with integer division is also made.
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Advanced Sql Interview Questions For Data Scientists
Check out this collection of advanced SQL interview questions with answers.
The standard language used for all databases is Structured Query Language.
It plays a key role to fetch the demandable data from the database. All the big data platforms like Hadoop, and Spark uses SQL as a high-level language for their organizations.
Data science is the only field of study and analysis of data. The outcomes of the data should be accurate and correct to perform a survey.
This is how SQL comes into the picture with data science. Though certain organizations have made a switch to NoSQL, the fundamentals lie in SQL.
Gearing up for a data science interview?
What Is Case In Sql
The CASE command is how you use if/then logic in SQL.
The CASE command is followed by a WHEN statement, which corresponds to the if in if/then logic. The WHEN clause sets a condition for the query. It then moves to the THEN part of the query, which defines what occurs if the condition is satisfied.
Read more about the use of CASE statements in SQL.
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What Is The Salary Of A Data Analytics Expert In Chicago
The average salary of a Data Analyst Expert in Chicago is $62,904/year. The salary varies due to a number of factors such as job location, years of experience, skillset, and most importantly, the company for which you are applying. Taking some Data Analytics courses in Chicago would help you learn and implement the different skills required for the role.
Define And Provide An Example Of Using An Inner Join
Its not all about theory. Using a hands-on approach to handling realistic tasks is often times way more important. Thats why youll have to deal with practical SQL interview questions, too.
Obviously, you must be aware that joins are one of the most frequently used tools in SQL, regardless of your job role. Particularly if you are working in the sphere of business intelligence, your work will be centred around understanding SQL joins in depth.
So, an SQL join is a tool that allows you to construct a relationship between objects in your database. Consequently, a join shows a result set containing fields derived from two or more tables.
For instance, assume that in one table you have data about the customer ID and fields related to the sales a customer has made, and in the other, you have data about the customer ID and their private information, such as first and last name and email address. Therefore, an inner join allows you to obtain an output containing information from both tables only for the customer IDs found in the two tables that match. Provided that you set the customer ID field to be a matching column, of course.
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What Are The Differences Between Mongodb And Sql
Here are the major differences between MongoDB and SQL:
- SQL databases are relational in nature whereas MongoDB has non-relational databases.
- SQL uses the commands and statements in the SQL query language. MongoDB uses JSON as its query language.
- SQL is vertically scalable, whereas MongoDB is horizontally scalable.
- SQL focuses on the properties of ACID: atomicity, consistency, isolation, and durability. MongoDB emphasizes CAP properties: consistency, availability, and partition tolerance.