Spinny Intern Interview Questions and Answers

Unique key allows null values, primary key does not.

• Primary key is a unique identifier for a record in a table

• Unique key allows null values, primary key does not

• A table can have only one primary key, but multiple unique keys

• Primary key is automatically indexed, unique key is not necessarily indexed

HAVING clause is used in SQL to filter data based on aggregate functions.

• It is used with GROUP BY clause to filter data based on aggregate functions

• It is used to filter data after grouping has been done

• It is similar to WHERE clause but operates on grouped data

• Example: SELECT department, AVG(salary) FROM employees GROUP BY department HAVING AVG(salary) > 50000;

LRU Cache is a data structure that stores the most recently used items and discards the least recently used items.

• Use a hash table to store key-value pairs

• Use a doubly linked list to keep track of the order of items

• When an item is accessed, move it to the front of the list

• When the cache is full, remove the least recently used item from the back of the list

• Lookup and insertion should be O(1) time complexity

Implement 2 stacks in an array

• Divide the array into two halves

• Use top1 and top2 to keep track of top elements of stacks

• Push and pop elements from respective halves

• Check for overflow and underflow conditions