Advertising on the Telegram channel «SQL for data analysis»

35 Important SQL Interview Questions with Detailed Answers: 1. Explain order of execution of SQL. Order: FROM → JOIN → ON → WHERE → GROUP BY → HAVING → SELECT → DISTINCT → ORDER BY → LIMIT. SQL queries are processed in this logical sequence, not the way they are written. 2. What is difference between WHERE and HAVING? WHERE filters rows before aggregation, while HAVING filters groups after aggregation. 3. What is the use of GROUP BY? GROUP BY aggregates data across rows with the same values in specified columns, commonly used with aggregate functions. 4. Explain all types of joins in SQL? INNER JOIN: Returns matching rows from both tables. LEFT JOIN: All rows from the left, matched rows from right. RIGHT JOIN: All rows from the right, matched rows from left. FULL JOIN: All rows from both, with NULLs where no match. SELF JOIN: Joins table to itself. CROSS JOIN: Cartesian product of both tables. 5. What are triggers in SQL? Triggers are procedural code executed automatically in response to certain events on a table or view (INSERT, UPDATE, DELETE). 6. What is stored procedure in SQL? A stored procedure is a set of SQL statements saved and executed on demand, useful for modularizing code. 7. Explain all types of window functions? RANK(): Gives rank with gaps. DENSE_RANK(): Ranks without gaps. ROW_NUMBER(): Unique row index. LEAD(): Access next row. LAG(): Access previous row. 8. What is difference between DELETE and TRUNCATE? DELETE: Row-wise deletion, can have WHERE clause, logs each row. TRUNCATE: Deletes all rows, faster, minimal logging, cannot rollback easily. 9. What is difference between DML, DDL and DCL? DML: Data Manipulation Language (SELECT, INSERT, UPDATE, DELETE). DDL: Data Definition Language (CREATE, ALTER, DROP). DCL: Data Control Language (GRANT, REVOKE). 10. What are aggregate functions? Functions that return a single value: SUM(), AVG(), COUNT(), MIN(), MAX(). 11. Which is faster: CTE or Subquery? Performance depends on context, but subqueries are sometimes faster as CTEs may be materialized. 12. What are constraints and types? Rules to maintain data integrity. Types: NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK, DEFAULT. 13. Types of Keys? Primary Key Foreign Key Unique Key Composite Key Candidate Key 14. Different types of Operators? Arithmetic: +, -, *, / Comparison: =, <>, >, <, >=, <= Logical: AND, OR, NOT Bitwise, LIKE, IN, BETWEEN 15. Difference between GROUP BY and WHERE? WHERE filters before aggregation. GROUP BY groups after filtering. 16. What are Views? Virtual tables based on SQL queries. They store only query definition. 17. What are different types of constraints? Same as Q12: NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK, DEFAULT. 18. What is difference between VARCHAR and NVARCHAR? VARCHAR: ASCII, 1 byte per char. NVARCHAR: Unicode, 2 bytes per char, supports multiple languages. 19. Similarity for CHAR and NCHAR? CHAR: Fixed-length ASCII. NCHAR: Fixed-length Unicode. 20. What are indexes and their types? Used for faster retrieval. Types: - Clustered - Non-clustered - Unique - Composite - Full-text 21. What is an index? Explain its types. Same as above. Indexes speed up queries by creating pointers to data. 22. List different types of relationships in SQL. One-to-One One-to-Many Many-to-Many 23. Differentiate between UNION and UNION ALL. UNION: Removes duplicates. UNION ALL: Includes duplicates. 24. How many types of clauses in SQL? Common clauses: SELECT, FROM, WHERE, GROUP BY, HAVING, ORDER BY, LIMIT, OFFSET, JOIN, ON. 25. What is the difference between UNION and UNION ALL in SQL? Same as Q23. 26. What are various types of relationships in SQL? Same as Q22. 27. Difference between Primary Key and Secondary Key? Primary Key: Uniquely identifies rows. Secondary Key: May not be unique, used for lookup. Credits: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v/1000

35 Most Common SQL Interview Questions 👇👇 1.) Explain order of execution of SQL. 2.) What is difference between where and having? 3.) What is the use of group by? 4.) Explain all types of joins in SQL? 5.) What are triggers in SQL? 6.) What is stored procedure in SQL 7.) Explain all types of window functions? (Mainly rank, row_num, dense_rank, lead & lag) 8.) What is difference between Delete and Truncate? 9.) What is difference between DML, DDL and DCL? 10.) What are aggregate function and when do we use them? explain with few example. 11.) Which is faster between CTE and Subquery? 12.) What are constraints and types of Constraints? 13.) Types of Keys? 14.) Different types of Operators ? 15.) Difference between Group By and Where? 16.) What are Views? 17.) What are different types of constraints? 18.) What is difference between varchar and nvarchar? 19.) Similar for char and nchar? 20.) What are index and their types? 21.) What is an index? Explain its different types. 22.) List the different types of relationships in SQL. 23.) Differentiate between UNION and UNION ALL. 24.) How many types of clauses in SQL? 25.) What is the difference between UNION and UNION ALL in SQL? 26.) What are the various types of relationships in SQL? 27.) Difference between Primary Key and Secondary Key? 28.) What is the difference between where and having? 29.) Find the second highest salary of an employee? 30.) Write retention query in SQL? 31.) Write year-on-year growth in SQL? 32.) Write a query for cummulative sum in SQL? 33.) Difference between Function and Store procedure ? 34.) Do we use variable in views? 35.) What are the limitations of views? React with ❤️ for the detailed answers

𝗠𝗮𝘀𝘁𝗲𝗿 𝗗𝗮𝘁𝗮 𝗔𝗻𝗮𝗹𝘆𝘁𝗶𝗰𝘀 & 𝗠𝗮𝗰𝗵𝗶𝗻𝗲 𝗟𝗲𝗮𝗿𝗻𝗶𝗻𝗴 𝗳𝗼𝗿 𝗙𝗿𝗲𝗲 𝘄𝗶𝘁𝗵 𝗠𝗶𝗰𝗿𝗼𝘀𝗼𝗳𝘁 𝗟𝗲𝗮𝗿𝗻𝗶𝗻𝗴 𝗣𝗮𝘁𝗵𝘀😍 Want to level up your Data Analytics & Machine Learning game—for FREE?🔥 These official Microsoft learning paths are your shortcut to building practical, job-ready skills. 🧠💻 𝐋𝐢𝐧𝐤👇:- https://pdlink.in/4cIU9cc Because your future job in data isn’t going to wait. Why should you? 🔥

Preparing for a SQL interview? Focus on mastering these essential topics: 1. Joins: Get comfortable with inner, left, right, and outer joins. Knowing when to use what kind of join is important! 2. Window Functions: Understand when to use ROW_NUMBER, RANK(), DENSE_RANK(), LAG, and LEAD for complex analytical queries. 3. Query Execution Order: Know the sequence from FROM to ORDER BY. This is crucial for writing efficient, error-free queries. 4. Common Table Expressions (CTEs): Use CTEs to simplify and structure complex queries for better readability. 5. Aggregations & Window Functions: Combine aggregate functions with window functions for in-depth data analysis. 6. Subqueries: Learn how to use subqueries effectively within main SQL statements for complex data manipulations. 7. Handling NULLs: Be adept at managing NULL values to ensure accurate data processing and avoid potential pitfalls. 8. Indexing: Understand how proper indexing can significantly boost query performance. 9. GROUP BY & HAVING: Master grouping data and filtering groups with HAVING to refine your query results. 10. String Manipulation Functions: Get familiar with string functions like CONCAT, SUBSTRING, and REPLACE to handle text data efficiently. 11. Set Operations: Know how to use UNION, INTERSECT, and EXCEPT to combine or compare result sets. 12. Optimizing Queries: Learn techniques to optimize your queries for performance, especially with large datasets. If we master/ Practice in these topics we can track any SQL interviews.. Like this post if you need more 👍❤️ Hope it helps :)

𝗧𝗼𝗽 𝗠𝗡𝗖𝘀 𝗛𝗶𝗿𝗶𝗻𝗴 𝗗𝗮𝘁𝗮 𝗔𝗻𝗮𝗹𝘆𝘀𝘁𝘀 😍 - Amazon - Infosys - PwC - Genpact - Deloitte Qualification :- Any Graduate  𝐑𝐞𝐠𝐢𝐬𝐭𝐞𝐫 & 𝐔𝐩𝐥𝐨𝐚𝐝 𝐘𝐨𝐮𝐫 𝐑𝐞𝐬𝐮𝐦𝐞👇:-   https://pdlink.in/44qEIDu Enter your experience & Complete The Registration Process Select the company name & Apply for jobs💫

SQL Interview Questions which can be asked in a Data Analyst Interview. 1️⃣ What is difference between Primary key and Unique key?         ◼Primary key- A column or set of columns which uniquely identifies each record in a table. It can't contain null values and only one primary key can exist in a table. ◼Unique key-Similar to primary key it also uniquely identifies each record in a table and can contain null values.Multiple Unique key can exist in a table. 2️⃣ What is a Candidate key? ◼A key or set of keys that uniquely identifies each record in a table.It is a combination of Primary and Alternate key. 3️⃣ What is a Constraint? ◼Specific rule or limit that we define in our table. E.g - NOT NULL,AUTO INCREMENT 4️⃣ Can you differentiate between TRUNCATE and DELETE? ◼TRUNCATE is a DDL command. It deletes the entire data from a table but preserves the structure of table.It doesn't deletes the data row by row hence faster than DELETE command, while DELETE is a DML command and it deletes the entire data based on specified condition else deletes the entire data,also it deletes the data row by row hence slower than TRUNCATE command. 5️⃣ What is difference between 'View' and 'Stored Procedure'? ◼A View is a virtual table that gets data from the base table .It is basically a Select statement,while Stored Procedure is a sql statement or set of sql statement stored on database server. 6️⃣ What is difference between a Common Table Expression and temporary table? ◼CTE is a temporary result set that is defined within execution scope of a single SELECT ,DELETE,UPDATE statement while temporary table is stored in TempDB and gets deleted  once the session expires. 7️⃣ Differentiate between a clustered index and a non-clustered index? ◼ A clustered index determines physical ordering of data in a table and a table can have only one clustered index while a non-clustered index is analogous to index of a book where index is stored at one place and data at other place and index will have pointers to storage location of the data,a table can have more than one non-clustered index. 8️⃣ Explain triggers ? ◼They are sql codes which are automatically executed in response to certain events on a table.They are used to maintain integrity of data.

🎰 Feeling Lucky? Get 20% Cashback at Fortunejack! 💸 🔥 Deposit 50 USDT and enjoy 20% Cashback — win or lose, we’ve got your back! 💰 Crypto gaming just got safer. Take your shot at the tables and spin the slots without the stress. 👉 Don’t miss out. Play smart. Get rewarded  🌐 Click The Link Fortunejack.com #CryptoCasino #Cashback #Fortunejack #USDT #CryptoGaming

Ad 👇👇

Important SQL Interview Questions and Answers (2025) 1. How do you find duplicate records in SQL? SELECT column_name, COUNT(*) FROM table_name GROUP BY column_name HAVING COUNT(*) > 1; This query groups records by a specific column and filters groups that have more than one occurrence. 2. What are the different types of SQL Joins? - INNER JOIN: Returns records that have matching values in both tables. - LEFT JOIN: Returns all records from the left table and the matched records from the right table. - RIGHT JOIN: Returns all records from the right table and the matched records from the left table. - FULL OUTER JOIN: Returns all records when there is a match in either left or right table. - SELF JOIN: A regular join but the table is joined with itself. 3. What is a Trigger in SQL? A trigger is a stored procedure that runs automatically in response to specific events on a particular table or view (e.g., INSERT, UPDATE, DELETE). 4. Differentiate between DDL and DML commands in SQL. DDL (Data Definition Language): Defines database schema (CREATE, ALTER, DROP). DML (Data Manipulation Language): Manipulates data (INSERT, UPDATE, DELETE). 5. Difference between DELETE, DROP, and TRUNCATE. DELETE: Removes specific rows, can use WHERE clause, can be rolled back. TRUNCATE: Removes all rows, faster than DELETE, cannot be rolled back in most DBMS. DROP: Deletes the entire table structure and data. 6. UNION vs UNION ALL – What’s the difference? UNION: Removes duplicate records. UNION ALL: Includes duplicates. 7. Which command gives unique values in SQL? SELECT DISTINCT column_name FROM table_name; 8. WHERE vs HAVING – Key differences? WHERE: Filters rows before grouping. HAVING: Filters groups after aggregation. 9. Explain the execution order of SQL keywords. 1. FROM 2. WHERE 3. GROUP BY 4. HAVING 5. SELECT 6. ORDER BY 7. LIMIT 10. IN vs BETWEEN operators – When to use what? IN: For checking values within a list. BETWEEN: For checking values within a range. 11. Define Primary Key and Foreign Key. Primary Key: Uniquely identifies each record in a table. Foreign Key: Links records between two tables. 12. What are Aggregate Functions in SQL? Functions like COUNT(), SUM(), AVG(), MAX(), MIN() used for calculations on data. 13. Difference between RANK and DENSE_RANK? RANK(): Leaves gaps in ranking when there are ties. DENSE_RANK(): No gaps in ranks. 14. List and explain ACID Properties. Atomicity: All or nothing. Consistency: Valid state before and after a transaction. Isolation: Transactions don't affect each other. Durability: Results are permanent after commit. 15. What is the difference between % and _ in LIKE operator? %: Matches any number of characters. _: Matches a single character. 16. What is CTE (Common Table Expression)? A temporary result set defined within the execution scope of a single SELECT, INSERT, UPDATE, or DELETE statement. WITH CTE AS ( SELECT column FROM table ) SELECT * FROM CTE; 17. What is a Database, DBMS, and RDBMS? Database: Organized data collection. DBMS: Software to manage databases. RDBMS: DBMS based on relational model (tables, keys). 18. What is an Alias in SQL? Temporary name for a table or column. SELECT column_name AS alias_name FROM table_name; 19. What is Normalization? Explain its types. Process of organizing data to reduce redundancy: 1NF: Eliminate repeating groups. 2NF: Remove partial dependency. 3NF: Remove transitive dependency. 20. How to sort query results in SQL? Use ORDER BY clause. SELECT * FROM table_name ORDER BY column_name ASC|DESC; 21. Explain types of Window Functions. ROW_NUMBER(), RANK(), DENSE_RANK(), NTILE(), LEAD(), LAG(), etc., work over a partition of data. 22. What is LIMIT and OFFSET in SQL? LIMIT: Specifies the number of records to return. OFFSET: Specifies how many rows to skip before starting to return rows. Credits: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

𝟱 𝗙𝗿𝗲𝗲 𝗥𝗲𝘀𝗼𝘂𝗿𝗰𝗲𝘀 𝗧𝗵𝗮𝘁’𝗹𝗹 𝗠𝗮𝗸𝗲 𝗦𝗤𝗟 𝗙𝗶𝗻𝗮𝗹𝗹𝘆 𝗖𝗹𝗶𝗰𝗸.😍 SQL seems tough, right? 😩 These 5 FREE SQL resources will take you from beginner to advanced without boring theory dumps or confusion.📊 𝐋𝐢𝐧𝐤👇:- https://pdlink.in/3GtntaC Master it with ease. 💡