1) How do you update a table with a large number of updates, while maintaining the availability of the table for a large number of users? (SQL)

2) Given a list of numbers [1,2,3,4,5,6,7,8,9], print all the pairs for which the summation of index positions is equal to 10. (Python / Java / C#)

3) Given a list of words, can you find out the frequency of each word? (Python / Java / C#)

4) How to optimize merge statement with millions of rows? (SQL)