Introduction
Although the development of SQL (Structured Query Language) dates back to the 1970s, it still remains relevant in today’s technically advanced era. Around 70% hiring managers consider SQL knowledge a must for data-related roles.
Therefore, if you choose this field, your in-depth understanding of its concepts will be tested during basic and advanced SQL interview questions. This detailed guide contains practice question sets of varying levels to help you start the preparation.
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Basic SQL Interview Questions
If you are new to SQL, you cannot risk missing the preparation for basic SQL interview questions. These are a must in every interview where the recruiter wants to gauge your grasp of the fundamental concepts.
Practice Questions:
Q1. Define SQL and mention its three main components.
Q2. Name the different SQL operators with two examples each.
Q3. Differentiate between a foreign key and a unique key.
Q4. What is the SELECT statement used for?
Q5. Define a subquery and state its use.
Advanced SQL Interview Questions
To showcase your understanding of the more complex SQL concepts, preparing for advanced SQL questions is equally important. Recruiters may consider asking these questions based on the experience level requirement of the position.
Practice Questions:
Q1. What is the use of UNION? How is it different from UNION ALL?
Q2. Name and explain the ACID properties.
Q3. Which operations do the MERGE statements combine? What is its main function?
Q4. List four ways for the optimisation of slow-running queries in SQL.
Q5. Differentiate between local and global variables.
SQL Aggregate Functions-Related Questions
Recruiters ask questions related to SQL aggregate functions to assess your data summarisation knowledge, analytical skills, and practical application, among other skills.
Practice Questions:
Q1. List the five most common SQL aggregate functions and state their use.
Q2. Differentiate between COUNT() and MAX() aggregate functions.
Q3. What is the syntax of an aggregate function?
Q4. How do aggregate functions differ from window functions?
Q5. What is the use of approximate aggregate functions? Mention three examples.
SQL Subquery Interview Questions
The SQL subquery is frequently used to construct efficient data queries, though the efficiency depends on various factors. Hence, they form an important part of the knowledge area which you should focus on for interviews.
Practice Questions:
Q1. What is the difference between a subquery and a derived table?
Q2. What is an IN operator? Differentiate it from an EXISTS operator.
Q3. Name the four types of subqueries in SQL.
Q4. What are non-correlated subqueries? How do they differ from correlated subqueries?
Q5. What are the uses of subqueries in data manipulation and data aggregation?
Also Read: Top 100 SQL & MySQL Interview Questions for Interview Prep
SQL Performance Interview Questions
The questions in an SQL performance interview can range from execution plans and indexing to database design principles and more. They test your technical readiness, critical thinking, and real-life application experience.
Practice Questions:
Q1. What is the role of indexes in improving query performance?
Q2. Mention five ways in which SQL query performance can be improved?
Q3. Define SQL performance tuning and state its importance.
Q4. List some of the main reasons impacting SQL speed.
Q5. Name some popular tools used for SQL performance tuning.
SQL Transaction Questions for Interview Practice
Recruiters often ask SQL transaction questions to test if you have the required knowledge of error handling, data integrity, and concurrency. As it is essential for maintaining a reliable database state, it should be one of your key must-know areas.
Practice Questions:
Q1. List 4 control commands of SQL transactions. What are they used for?
Q2. What is the technical term used for manually controlled transactions? Mention the main commands used in it.
Q3. What are the commonly known SQL transaction challenges? Give one solution for each.
Q4. Mention 2 scenarios where an SQL transaction can be used.
Q5. What are nested transactions?
SQL Analytics Interview Questions
Questions surrounding SQL analytics are generally asked by recruiters to check your proficiency in data manipulation and analysis. This is another key area to prove your potential for roles requiring SQL analytics knowledge.
Practice Questions:
Q1. Differentiate between DAU and MAU.
Q2. List the ways in which SQL can be used to find high-engagement users.
Q3. What is a WHERE clause? How does it differ from the HAVING clause?
Q4. Briefly explain how SQL can be used to categorise users based on activity frequency.
Q5. How would you use SQL to measure success metrics?
SQL Coding Interview Questions
Besides assessing your basic knowledge, SQL coding questions help recruiters check your ability to write queries. This is essential as technical positions demand this skill.
Practice Questions:
Q1. Write a query to find the student ID who did not receive a scholarship.
Q2. Write a query for getting the last 3 records from a table.
Q3.Write a query to calculate the sum of entries in a table’s column.
Q4. Write a query to look up the highest GPA in a given table.
Q5. Write a query for displaying the current time.
Tips for SQL Interview Preparation
In spite of all the readiness, SQL interviews can at times feel intimidating. However, the following tips can help you prepare well and overcome interview anxiety:
Seek Clarification Where Required
Before answering any question, make sure you have understood it fully. If you feel that any additional details are required before answering, ask for them.
Prepare Basic and Advanced Questions
To ensure your readiness for different types of questions, practice answering questions from a mix of various question difficulty levels.
Practice Explaining Your Query
After writing down an SQL query, the interviewer may even ask you to explain the logic behind it. Hence, be ready for counter-questioning.
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Conclusion
The trickiest part of appearing for technical interviews is that they are multifaceted. From basic and advanced to practical, you will come across different types of questions based on the position and level you are applying for. Hence, using this guide, you can find the list of important questions to prepare for and excel.
For upskilling yourself in this field, you can consider enrolling for the related short-term certification courses offered by Amity University Online.
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