SQL Interview Questions

1. Can you explain the difference between a primary key and a foreign key in a relational database?
2. How do you design a database schema for a new application?
3. How do you write a SQL query to select specific columns and rows from a table?
4. Can you explain the difference between a left join and a right join?
5. How do you write a SQL query to update or delete specific rows in a table?
6. Can you explain how indexes work in a relational database and why they are important?
7. How do you write a SQL query to find duplicate rows in a table?
8. Can you explain how transactions work in SQL and how they are used to ensure data consistency?
9. How do you write a SQL query to retrieve data from multiple tables using a join?
10. Can you explain the difference between a subquery and a join?
11. How do you write a SQL query to create a new table and insert data into it?
12. Can you explain how views work in SQL and when they should be used?
13. How do you write a SQL query to group data by certain columns and calculate aggregate functions?
14. Can you explain the difference between a clustered and non-clustered index?
15. How do you optimize a slow SQL query?
16. Can you explain the difference between SQL and NoSQL databases?
17. How do you write a SQL query to create a stored procedure?
18. Can you explain the difference between a temporary table and a table variable?
19. How do you write a SQL query to create a trigger?
20. Can you explain the difference between a union and a union all in SQL?