1. Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.
2. Write code for searching in a 2D matrix with a time complexity of O(mlogn).
3. Write an SQL query to find the second highest salary from the Employee table.
4. What are Joins?
5. Given an array containing only 0s, 1s, and 2s, sort the array in-place.