The best place to start you preparation if you already know basic of python and SQL is Glassdoor questions. I have complied and solved all the Python question. I will try to attach a link later to this review. I solved all the python questions given. it was a repetition of the questions mentioned already in glassdoor. What i underestimated is the time to handle all the test cases. The code you write can easily solve the problem question, it takes 6 to 8 mins to type out the code. but there will be 5 test cases. the code will not handle all the 5 test cases. only if all the 5 test cases pass the next question will be given. A easy problem given to me was replace the Null with previous value in list. The test case will have string instead of list. the first value of list will be null, there will be empty list. So your code has to handle all of these test cases. SQL: I wasn't great at postgres so I couldn't reach the output even though the logic was right. Please prepare SQL coding of glassdoor question with Postgres. in a table find the percentage of customers who purchased a particular product.