#Sql

Write an SQL query to extract the third transaction of every user, displaying user ID, spend, and transaction date.

Discuss the differences and applications of SQL and NoSQL databases.

Describe what composite indexing is in databases. Provide examples of how and when it should be used effectively.

Discuss your approach to optimizing a slow SQL query. What steps would you take, and what tools would you use?

Write an SQL query to find the second-highest salary from an employee table. The table contains a column 'salary'.