Here are the SQL interview questions:

Basic SQL Questions

1.⁠ ⁠What is SQL, and what is its purpose?
2.⁠ ⁠Write a SQL query to retrieve all records from a table.
3.⁠ ⁠How do you select specific columns from a table?
4.⁠ ⁠What is the difference between WHERE and HAVING clauses?
5.⁠ ⁠How do you sort data in ascending/descending order?


SQL Query Questions

1.⁠ ⁠Write a SQL query to retrieve the top 10 records from a table based on a specific column.
2.⁠ ⁠How do you join two tables based on a common column?
3.⁠ ⁠Write a SQL query to retrieve data from multiple tables using subqueries.
4.⁠ ⁠How do you use aggregate functions (SUM, AVG, MAX, MIN)?
5.⁠ ⁠Write a SQL query to retrieve data from a table for a specific date range.


SQL Optimization Questions

1.⁠ ⁠How do you optimize SQL query performance?
2.⁠ ⁠What is indexing, and how does it improve query performance?
3.⁠ ⁠How do you avoid full table scans?
4.⁠ ⁠What is query caching, and how does it work?
5.⁠ ⁠How do you optimize SQL queries for large datasets?


SQL Joins and Subqueries

1.⁠ ⁠Explain the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.
2.⁠ ⁠Write a SQL query to retrieve data from two tables using a subquery.
3.⁠ ⁠How do you use EXISTS and IN operators in SQL?
4.⁠ ⁠Write a SQL query to retrieve data from multiple tables using a self-join.
5.⁠ ⁠Explain the concept of correlated subqueries.


SQL Data Modeling

1.⁠ ⁠Explain the concept of normalization and denormalization.
2.⁠ ⁠How do you design a database schema for a given application?
3.⁠ ⁠What is data redundancy, and how do you avoid it?
4.⁠ ⁠Explain the concept of primary and foreign keys.
5.⁠ ⁠How do you handle data inconsistencies and anomalies?


SQL Advanced Questions

1.⁠ ⁠Explain the concept of window functions (ROW_NUMBER, RANK, etc.).
2.⁠ ⁠Write a SQL query to retrieve data using Common Table Expressions (CTEs).
3.⁠ ⁠How do you use dynamic SQL?
4.⁠ ⁠Explain the concept of stored procedures and functions.
5.⁠ ⁠Write a SQL query to retrieve data using pivot tables.


SQL Scenario-Based Questions

1.⁠ ⁠You have two tables, Orders and Customers. Write a SQL query to retrieve all orders for customers from a specific region.
2.⁠ ⁠You have a table with duplicate records. Write a SQL query to remove duplicates.
3.⁠ ⁠You have a table with missing values. Write a SQL query to replace missing values with a default value.
4.⁠ ⁠You have a table with data in an incorrect format. Write a SQL query to correct the format.
5.⁠ ⁠You have two tables with different data types for a common column. Write a SQL query to join the tables.


SQL Behavioral Questions

1.⁠ ⁠Can you explain a time when you optimized a slow-running SQL query?
2.⁠ ⁠How do you handle database errors and exceptions?
3.⁠ ⁠Can you describe a complex SQL query you wrote and why?
4.⁠ ⁠How do you stay up-to-date with new SQL features and best practices?
5.⁠ ⁠Can you walk me through your process for troubleshooting SQL issues?