{"id":52137,"date":"2025-06-18T17:17:29","date_gmt":"2025-06-18T11:47:29","guid":{"rendered":"https:\/\/www.iquanta.in\/blog\/?p=52137"},"modified":"2025-06-18T17:17:31","modified_gmt":"2025-06-18T11:47:31","slug":"top-30-sql-interview-questions-and-answers","status":"publish","type":"post","link":"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/","title":{"rendered":"Top 30 SQL Interview Questions and Answers"},"content":{"rendered":"\n<p>Are you seriously preparing for data related roles and wants to ace interview?. Then this blog really helps you to prepare highly asked Language in such roles that is SQL. Whether you are applying for a Data Analyst, Database Administrator or Software Developer roles, SQL requires to basically testing your skills. <\/p>\n\n\n\n<p>In this blog we will be talking about the top 30 SQL interview questions and answers in detail so that you will fully prepared for your next interview. These questions varies and starting for the beginners and goes for the experienced too. So, Let us begin this blog to start with your interview journey. <\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_77 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_SQL\" >What is SQL?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Top_30_SQL_Interview_Questions_and_Answers\" >Top 30 SQL Interview Questions and Answers<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Beginner-Level_SQL_Interview_Questions\" >Beginner-Level SQL Interview Questions<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_the_difference_between_SQL_and_MySQL\" >What is the difference between SQL and MySQL?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_are_the_different_types_of_SQL_Commands\" >What are the different types of SQL Commands?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_a_primary_key\" >What is a primary key?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_a_foreign_key\" >What is a foreign key?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_the_difference_between_WHERE_and_HAVING_clause\" >What is the difference between WHERE and HAVING clause?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_a_JOIN_Name_different_types\" >What is a JOIN? Name different types.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_the_difference_between_INNER_JOIN_and_LEFT_JOIN\" >What is the difference between INNER JOIN and LEFT JOIN?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_normalization\" >What is normalization?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_is_denormalization\" >What is denormalization?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#What_are_the_different_normal_forms\" >What are the different normal forms?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Intermediate-Level_SQL_Interview_Questions\" >Intermediate-Level SQL Interview Questions<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_find_the_second_highest_salary_from_the_Employee_table\" >Write a query to find the second highest salary from the Employee table.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_display_each_departments_name_with_the_total_number_of_employees_in_it\" >Write a query to display each department&#8217;s name with the total number of employees in it.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_find_employees_who_joined_in_the_last_3_months\" >Write a query to find employees who joined in the last 3 months.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_fetch_duplicate_email_records_from_the_Users_table\" >Write a query to fetch duplicate email records from the Users table.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_find_the_top_3_departments_with_the_highest_average_salary\" >Write a query to find the top 3 departments with the highest average salary.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_fetch_employee_names_that_start_and_end_with_a_vowel\" >Write a query to fetch employee names that start and end with a vowel.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_calculate_the_running_total_of_sales_per_day\" >Write a query to calculate the running total of sales per day.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_find_customers_who_placed_more_than_two_orders_in_the_last_30_days\" >Write a query to find customers who placed more than two orders in the last 30 days.<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_pivot_monthly_sales_data_into_columns_Jan_Feb_Mar_%E2%80%A6\" >Write a query to pivot monthly sales data into columns (Jan, Feb, Mar, \u2026).<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-24\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Write_a_query_to_find_employees_earning_more_than_the_average_salary_in_their_department\" >Write a query to find employees earning more than the average salary in their department.<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-25\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Advanced-Level_SQL_Interview_Questions\" >Advanced-Level SQL Interview Questions<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-26\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Why_SQL_Interview_Questions_Are_Important_for_Data_Roles\" >Why SQL Interview Questions Are Important for Data Roles?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-27\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#How_Non-Tech_People_Prepare_For_SQL_Interview_Questions\" >How Non-Tech People Prepare For SQL Interview Questions?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-28\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#Conclusion\" >Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\" id=\"h-what-is-sql\"><span class=\"ez-toc-section\" id=\"What_is_SQL\"><\/span><strong>What is SQL?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>SQL stands for Structured Query Language. SQL queries used by many databases and it is helpful in performing several tasks such as updating, deletion, retrieve or many more CRUD operations. There are different databases like MySQL, PostgreSQL, Oracle and Microsoft SQL Server.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/chat.whatsapp.com\/B6weknl7133BQXjPva0pgB\"><img fetchpriority=\"high\" decoding=\"async\" width=\"864\" height=\"129\" src=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-136.png\" alt=\"SQL Interview Questions\" class=\"wp-image-52081\" srcset=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-136.png 864w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-136-300x45.png 300w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-136-768x115.png 768w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-136-150x22.png 150w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-136-696x104.png 696w\" sizes=\"(max-width: 864px) 100vw, 864px\" \/><\/a><\/figure><\/div>\n\n\n<h2 class=\"wp-block-heading\" id=\"h-top-30-sql-interview-questions-and-answers\"><span class=\"ez-toc-section\" id=\"Top_30_SQL_Interview_Questions_and_Answers\"><\/span><strong>Top 30 SQL Interview Questions and Answers<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>In this section we will see different SQL interview questions that is categorized into beginner -level, intermediate-level and advanced-level SQL interview questions.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-beginner-level-sql-interview-questions\"><span class=\"ez-toc-section\" id=\"Beginner-Level_SQL_Interview_Questions\"><\/span><strong>Beginner-Level SQL Interview Questions<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-the-difference-between-sql-and-mysql\"><span class=\"ez-toc-section\" id=\"What_is_the_difference_between_SQL_and_MySQL\"><\/span><strong>What is the difference between SQL and MySQL?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>SQL is a language used to manage and query relational databases. MySQL is an open-source RDBMS that uses SQL as its standard language.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large is-resized\"><img decoding=\"async\" width=\"1024\" height=\"1024\" src=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-1024x1024.jpg\" alt=\"SQL Interview Questions\" class=\"wp-image-52144\" style=\"width:577px;height:auto\" srcset=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-1024x1024.jpg 1024w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-300x300.jpg 300w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-150x150.jpg 150w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-768x768.jpg 768w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-1536x1536.jpg 1536w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-420x420.jpg 420w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-696x696.jpg 696w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-1068x1068.jpg 1068w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1-1920x1920.jpg 1920w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/6543131-1.jpg 2000w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure><\/div>\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-are-the-different-types-of-sql-commands\"><span class=\"ez-toc-section\" id=\"What_are_the_different_types_of_SQL_Commands\"><\/span><strong>What are the different types of SQL Commands?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>DDL (Data Definition Language): CREATE, DROP, ALTER<\/p>\n\n\n\n<p>DML (Data Manipulation Language): SELECT, INSERT, UPDATE, DELETE<\/p>\n\n\n\n<p>DCL (Data Control Language): GRANT, REVOKE<\/p>\n\n\n\n<p>TCL (Transaction Control Language): COMMIT, ROLLBACK, SAVEPOINT<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-a-primary-key\"><span class=\"ez-toc-section\" id=\"What_is_a_primary_key\"><\/span><strong>What is a primary key?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>A primary key uniquely identifies each record in a table. It cannot contain NULL values and must contain unique values.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-a-foreign-key\"><span class=\"ez-toc-section\" id=\"What_is_a_foreign_key\"><\/span><strong>What is a foreign key?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>A foreign key is a field in one table that refers to the primary key in another table, establishing a relationship between the two.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-the-difference-between-where-and-having-clause\"><span class=\"ez-toc-section\" id=\"What_is_the_difference_between_WHERE_and_HAVING_clause\"><\/span><strong>What is the difference between WHERE and HAVING clause?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>WHERE filters rows before grouping.<\/p>\n\n\n\n<p>HAVING filters groups after the aggregation is done.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-a-join-name-different-types\"><span class=\"ez-toc-section\" id=\"What_is_a_JOIN_Name_different_types\"><\/span><strong>What is a JOIN? Name different types.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>A JOIN is used to combine rows from two or more tables based on a related column.<\/p>\n\n\n\n<ul>\n<li>INNER JOIN<\/li>\n\n\n\n<li>LEFT JOIN<\/li>\n\n\n\n<li>RIGHT JOIN<\/li>\n\n\n\n<li>FULL OUTER JOIN<\/li>\n\n\n\n<li>CROSS JOIN<\/li>\n<\/ul>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/chat.whatsapp.com\/B6weknl7133BQXjPva0pgB\"><img decoding=\"async\" width=\"864\" height=\"129\" src=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-140.png\" alt=\"\" class=\"wp-image-52161\" srcset=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-140.png 864w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-140-300x45.png 300w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-140-768x115.png 768w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-140-150x22.png 150w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-140-696x104.png 696w\" sizes=\"(max-width: 864px) 100vw, 864px\" \/><\/a><\/figure><\/div>\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-the-difference-between-inner-join-and-left-join\"><span class=\"ez-toc-section\" id=\"What_is_the_difference_between_INNER_JOIN_and_LEFT_JOIN\"><\/span><strong>What is the difference between INNER JOIN and LEFT JOIN?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>INNER JOIN returns only matching rows.<\/p>\n\n\n\n<p>LEFT JOIN returns all rows from the left table and matched rows from the right.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-normalization\"><span class=\"ez-toc-section\" id=\"What_is_normalization\"><\/span><strong>What is normalization?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>Normalization is the process of organizing data to minimize redundancy and improve data integrity.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-is-denormalization\"><span class=\"ez-toc-section\" id=\"What_is_denormalization\"><\/span><strong>What is denormalization?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>Denormalization is the process of adding redundant data to improve read performance.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-what-are-the-different-normal-forms\"><span class=\"ez-toc-section\" id=\"What_are_the_different_normal_forms\"><\/span><strong>What are the different normal forms?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<p>1NF: Atomic columns<\/p>\n\n\n\n<p>2NF: No partial dependency<\/p>\n\n\n\n<p>3NF: No transitive dependency<\/p>\n\n\n\n<p>BCNF: Enhanced 3NF<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-intermediate-level-sql-interview-questions\"><span class=\"ez-toc-section\" id=\"Intermediate-Level_SQL_Interview_Questions\"><\/span><strong>Intermediate-Level <a href=\"https:\/\/www.iquanta.in\/blog\/sql-vs-mysql-explained-with-examples\/\">SQL<\/a> Interview Questions<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>employee_id<\/td><td>name<\/td><td>department_id<\/td><td>salary<\/td><td>email<\/td><td>joining_date<\/td><\/tr><tr><td>101<\/td><td>Alice Johnson<\/td><td>1<\/td><td>75000<\/td><td><a href=\"mailto:alice.johnson@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">alice.johnson@abc.com<\/a><\/td><td>2024-09-12<\/td><\/tr><tr><td>102<\/td><td>Bob Smith<\/td><td>2<\/td><td>60000<\/td><td><a href=\"mailto:bob.smith@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">bob.smith@abc.com<\/a><\/td><td>2023-12-01<\/td><\/tr><tr><td>103<\/td><td>Charlie Lee<\/td><td>1<\/td><td>80000<\/td><td><a href=\"mailto:charlie.lee@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">charlie.lee@abc.com<\/a><\/td><td>2025-02-15<\/td><\/tr><tr><td>104<\/td><td>Diana Prince<\/td><td>3<\/td><td>90000<\/td><td><a href=\"mailto:diana.prince@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">diana.prince@abc.com<\/a><\/td><td>2022-07-21<\/td><\/tr><tr><td>105<\/td><td>Edward Cullen<\/td><td>2<\/td><td>60000<\/td><td><a href=\"mailto:edward.cullen@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">edward.cullen@abc.com<\/a><\/td><td>2025-03-05<\/td><\/tr><tr><td>106<\/td><td>Fiona Watson<\/td><td>1<\/td><td>85000<\/td><td><a href=\"mailto:fiona.watson@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">fiona.watson@abc.com<\/a><\/td><td>2025-04-10<\/td><\/tr><tr><td>107<\/td><td>George Martin<\/td><td>3<\/td><td>95000<\/td><td><a href=\"mailto:george.martin@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">george.martin@abc.com<\/a><\/td><td>2024-06-25<\/td><\/tr><tr><td>108<\/td><td>Helen Carter<\/td><td>2<\/td><td>60000<\/td><td><a href=\"mailto:helen.carter@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">helen.carter@abc.com<\/a><\/td><td>2023-11-10<\/td><\/tr><tr><td>109<\/td><td>Ivan Wright<\/td><td>3<\/td><td>91000<\/td><td><a href=\"mailto:ivan.wright@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">ivan.wright@abc.com<\/a><\/td><td>2025-01-12<\/td><\/tr><tr><td>110<\/td><td>Jane Doe<\/td><td>1<\/td><td>80000<\/td><td><a href=\"mailto:jane.doe@abc.com\" target=\"_blank\" rel=\"noreferrer noopener\">jane.doe@abc.com<\/a><\/td><td>2025-05-20<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-find-the-second-highest-salary-from-the-employee-table\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_find_the_second_highest_salary_from_the_Employee_table\"><\/span><strong>Write a query to find the second highest salary from the Employee table.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT MAX(salary) AS SecondHighestSalary\r\nFROM Employee\r\nWHERE salary &lt; (SELECT MAX(salary) FROM Employee);\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-display-each-department-s-name-with-the-total-number-of-employees-in-it\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_display_each_departments_name_with_the_total_number_of_employees_in_it\"><\/span><strong>Write a query to display each department&#8217;s name with the total number of employees in it.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT d.department_name, COUNT(e.employee_id) AS total_employees\r\nFROM Employee e\r\nJOIN Department d ON e.department_id = d.department_id\r\nGROUP BY d.department_name;\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-find-employees-who-joined-in-the-last-3-months\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_find_employees_who_joined_in_the_last_3_months\"><\/span><strong>Write a query to find employees who joined in the last 3 months.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT *\r\nFROM Employee\r\nWHERE joining_date &gt;= DATE_SUB(CURDATE(), INTERVAL 3 MONTH);\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-fetch-duplicate-email-records-from-the-users-table\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_fetch_duplicate_email_records_from_the_Users_table\"><\/span><strong>Write a query to fetch duplicate email records from the Users table.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT email, COUNT(*) AS count\r\nFROM Users\r\nGROUP BY email\r\nHAVING COUNT(*) &gt; 1;\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-find-the-top-3-departments-with-the-highest-average-salary\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_find_the_top_3_departments_with_the_highest_average_salary\"><\/span><strong>Write a query to find the top 3 departments with the highest average salary.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT d.department_name, AVG(e.salary) AS avg_salary\r\nFROM Employee e\r\nJOIN Department d ON e.department_id = d.department_id\r\nGROUP BY d.department_name\r\nORDER BY avg_salary DESC\r\nLIMIT 3;\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-fetch-employee-names-that-start-and-end-with-a-vowel\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_fetch_employee_names_that_start_and_end_with_a_vowel\"><\/span><strong>Write a query to fetch employee names that start and end with a vowel.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT name\r\nFROM Employee\r\nWHERE name REGEXP '^&#091;aeiouAEIOU].*&#091;aeiouAEIOU]$';\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-calculate-the-running-total-of-sales-per-day\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_calculate_the_running_total_of_sales_per_day\"><\/span><strong>Write a query to calculate the running total of sales per day.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT sale_date, amount,\r\n       SUM(amount) OVER (ORDER BY sale_date) AS running_total\r\nFROM Sales;\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-find-customers-who-placed-more-than-two-orders-in-the-last-30-days\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_find_customers_who_placed_more_than_two_orders_in_the_last_30_days\"><\/span><strong>Write a query to find customers who placed more than two orders in the last 30 days.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT customer_id, COUNT(order_id) AS order_count\r\nFROM Orders\r\nWHERE order_date &gt;= DATE_SUB(CURDATE(), INTERVAL 30 DAY)\r\nGROUP BY customer_id\r\nHAVING COUNT(order_id) &gt; 2;\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-pivot-monthly-sales-data-into-columns-jan-feb-mar\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_pivot_monthly_sales_data_into_columns_Jan_Feb_Mar_%E2%80%A6\"><\/span><strong>Write a query to pivot monthly sales data into columns (Jan, Feb, Mar, \u2026).<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT product_id,\r\n       SUM(CASE WHEN MONTH(sale_date) = 1 THEN amount ELSE 0 END) AS Jan,\r\n       SUM(CASE WHEN MONTH(sale_date) = 2 THEN amount ELSE 0 END) AS Feb,\r\n       SUM(CASE WHEN MONTH(sale_date) = 3 THEN amount ELSE 0 END) AS Mar\r\nFROM Sales\r\nGROUP BY product_id;\r<\/code><\/pre>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-write-a-query-to-find-employees-earning-more-than-the-average-salary-in-their-department\"><span class=\"ez-toc-section\" id=\"Write_a_query_to_find_employees_earning_more_than_the_average_salary_in_their_department\"><\/span><strong>Write a query to find employees earning more than the average salary in their department.<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h4>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT e.employee_id, e.name, e.salary, e.department_id\r\nFROM Employee e\r\nWHERE salary &gt; (\r\n    SELECT AVG(salary)\r\n    FROM Employee\r\n    WHERE department_id = e.department_id\r\n);\r<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-advanced-level-sql-interview-questions\"><span class=\"ez-toc-section\" id=\"Advanced-Level_SQL_Interview_Questions\"><\/span><strong>Advanced-Level SQL Interview Questions<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>No.<\/td><td>Advanced SQL Interview Question<\/td><\/tr><tr><td>1<\/td><td>How do you optimize a slow-running SQL query in a large dataset?<\/td><\/tr><tr><td>2<\/td><td>Write a query using a recursive Common Table Expression (CTE) to find the factorial of a number.<\/td><\/tr><tr><td>3<\/td><td>How would you write a query to detect gaps in a sequence of IDs in a table?<\/td><\/tr><tr><td>4<\/td><td>Explain and demonstrate the use of window functions like LEAD() and LAG() with an example.<\/td><\/tr><tr><td>5<\/td><td>How do you pivot and unpivot data in SQL without using built-in PIVOT\/UNPIVOT operators?<\/td><\/tr><tr><td>6<\/td><td>Write a query to rank items within categories and retrieve the top 2 in each group.<\/td><\/tr><tr><td>7<\/td><td>How do you handle performance tuning in SQL when working with joins on large tables?<\/td><\/tr><tr><td>8<\/td><td>Write a query to compare two tables and find mismatched records across all columns.<\/td><\/tr><tr><td>9<\/td><td>What are materialized views and how do they differ from regular views? When would you use them?<\/td><\/tr><tr><td>10<\/td><td>How do you implement Slowly Changing Dimensions (Type 2) in SQL for a data warehouse system?<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><a href=\"https:\/\/chat.whatsapp.com\/B6weknl7133BQXjPva0pgB\"><img loading=\"lazy\" decoding=\"async\" width=\"864\" height=\"129\" src=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-141.png\" alt=\"\" class=\"wp-image-52162\" srcset=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-141.png 864w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-141-300x45.png 300w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-141-768x115.png 768w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-141-150x22.png 150w, https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/image-141-696x104.png 696w\" sizes=\"(max-width: 864px) 100vw, 864px\" \/><\/a><\/figure><\/div>\n\n\n<h2 class=\"wp-block-heading\" id=\"h-why-sql-interview-questions-are-important-for-data-roles\"><span class=\"ez-toc-section\" id=\"Why_SQL_Interview_Questions_Are_Important_for_Data_Roles\"><\/span><strong>Why SQL Interview Questions Are Important for Data Roles?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>SQL is essential in any data-focused position, whether you are a data analyst, data engineer, business intelligence developer, or data scientist. <a href=\"https:\/\/www.iquanta.in\/blog\/sql-vs-mysql-explained-with-examples\/\">SQL questions <\/a>in interviews aim to evaluate your proficiency in efficiently retrieving, manipulating, and analyzing data through practical business scenarios.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-how-non-tech-people-prepare-for-sql-interview-questions\"><span class=\"ez-toc-section\" id=\"How_Non-Tech_People_Prepare_For_SQL_Interview_Questions\"><\/span><strong>How Non-Tech People Prepare For SQL Interview Questions?<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Non-technical professionals can successfully prepare for SQL interview questions by starting with the basics and using real-world examples to grasp core concepts. Since they may not have a programming background, it&#8217;s best to begin with understanding what databases are, how tables are structured, and how data is retrieved using simple SELECT statements.<\/p>\n\n\n\n<p>Free platforms and YouTube tutorials offer beginner-friendly SQL lessons. Once comfortable, they can move on to practice platforms like LeetCode (Easy level), HackerRank.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-conclusion\"><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span><strong>Conclusion<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>SQL is an important skill for anyone working with data, whether you are aiming for a role as a data analyst, engineer, or even a non-tech professional entering to the data field. So as to mastering SQL interview questions not only improves your ability to work with databases but also boosts your confidence during technical interviews. From basic queries to advanced concepts like window functions and performance tuning, consistent practice and real world problem solving are key for anyone. No matter your background is with the right preparation and mindset you can crack any SQL interview and take a step closer to your data career goals.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Are you seriously preparing for data related roles and wants to ace interview?. Then this blog really helps you to prepare highly asked Language in such roles that is SQL. Whether you are applying for a Data Analyst, Database Administrator or Software Developer roles, SQL requires to basically testing your skills. In this blog we [&hellip;]<\/p>\n","protected":false},"author":560,"featured_media":52142,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1074,1073],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.4 (Yoast SEO v21.9.1) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Top 30 SQL Interview Questions and Answers - iQuanta<\/title>\n<meta name=\"description\" content=\"In this blog we will be talking about the top 30 SQL interview questions and answers in detail so that you will fully prepared....\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Top 30 SQL Interview Questions and Answers\" \/>\n<meta property=\"og:description\" content=\"In this blog we will be talking about the top 30 SQL interview questions and answers in detail so that you will fully prepared....\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/\" \/>\n<meta property=\"og:site_name\" content=\"iQuanta\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/facebook.com\/iquanta.in\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-18T11:47:29+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2025-06-18T11:47:31+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.iquanta.in\/blog\/wp-content\/uploads\/2025\/06\/Your-paragraph-text-48.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1600\" \/>\n\t<meta property=\"og:image:height\" content=\"900\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Nidhi Goswami\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Nidhi Goswami\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"6 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/\"},\"author\":{\"name\":\"Nidhi Goswami\",\"@id\":\"https:\/\/www.iquanta.in\/blog\/#\/schema\/person\/ec8c8c25d0526dd86557b6fed064f7f3\"},\"headline\":\"Top 30 SQL Interview Questions and Answers\",\"datePublished\":\"2025-06-18T11:47:29+00:00\",\"dateModified\":\"2025-06-18T11:47:31+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/\"},\"wordCount\":1078,\"publisher\":{\"@id\":\"https:\/\/www.iquanta.in\/blog\/#organization\"},\"articleSection\":[\"Data Analytics\",\"iSkills\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/\",\"url\":\"https:\/\/www.iquanta.in\/blog\/top-30-sql-interview-questions-and-answers\/\",\"name\":\"Top 30 SQL Interview Questions and Answers - 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