4 Ways to find Nth highest salary in SQL - Oracle, MSSQL and MySQL

One of the most common SQL interview questions is to find the Nth highest salary of employees, where N could be 2, 3, 4 or anything e.g. find the second highest salary in SQL. Sometimes this question is also twisted as to find the nth minimum salary in SQL. Since many Programmers only know the easy way to solve this problem e.g. by using SQL IN clause, which doesn't scale well, they struggle to write the SQL query when the Interviewer keeps asking about the 4th highest, 5th highest and so on. In order to solve this problem effectively, you need to know about some key concepts like a correlated subquery, window functions like ROW_NUMER(), RANK(), and DENSE_RANK(), etc. Once you know the generic logic to solve this problem, you can tackle all those variations by yourself.

Difference between application/x-www-form-urlencoded and multipart/form-data in HTTP/HTML?

Recently in one of the Java web developer interview, one of my readers asked about the difference between x-www-form-url-encoded and multipart/form-data MIME types. In HTTP, there are two ways to send the HTML form data to the server either by using ContentType application/x-www-form-urlencoded or by using multipart/form-data. Even though both can be used to send both text and binary data to the server there is a subtle difference between them. In the case of x-www-form-urlencoded, the whole form data is sent as a long query string.

How to check for NULL values in SQL Query? The Right way Example

One of the most common SQL Interview question on Programming interview is to select some rows from a table which also contains null values. Since many SQL developers are used to using = and != operator on WHERE clause, they often tend to forget the fact that column allows NULL or not. Using = or != is perfectly fine if your column has NOT NULL constraint and you know for sure that there are no NULL values in that column, but it does contain NULLs then your query will return the incorrect result at times. This is one of the most common mistakes but at the same time hard to find SQL bugs if it managed to get into the real environment. In this article, you will learn the right way to check NULL values in SQL queries using IS NULL and IS NOT NULL predicates.

Top 20 Books Java Programmers Can Read in 2021

Hello guys, Happy New Year 2021. We are already in New Year and while I am busy making my goals for 2021, I am also looking back on what I have done in the last year. One of the things which I would like to share with you guys is some of the books I have read last year on Java and related technologies and will continue to read in 2021. This includes books on Modern Java, Spring, Hibernate, Object-oriented programming, Algorithms, Soft skills, Microservice, Groovy, Scala, Agile, and UML, etc. If you haven't read them yet, you can very well read them this year, depending on what technologies and programming languages you are going to learn in 2021.