Interview Question: Select only Prime numbers from table

Interview Questions, MSSQL, MySQL

As part of my daytime job, I conduct professional interviews for candidates. For that, I’m always on the search for good interview questions. I regard a good question if it’s not too complicated, has a number of ways to solve, and if needed, can be solved programmatically with SQL or C / C# / JAVA languages.

Now that I’m done with asking the prime number question (I need to change questions every now and then), I thought I will post the solution here.

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Calculate average time from DateTime MySql

MySQL

Calculating average time from DateTime field in MySql might come in handy in cases like getting the average arrival time, departure time, service sampling etc. In my case, I have a database with records on my arrival to work, and I wanted to calculate time average time that I arrive by the office, and then calculate how much time I spend in traffic, depending on when I leave my home.

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Prevent cookie hijacking (session hacking)

PHP

First of all, what is “Cookie Hijacking”?

By Wikipedia, it’s an “exploitation of a valid computer session to gain unauthorized access to information or services in a computer system. In particular, it is used to refer to the theft of a magic cookie used to authenticate a user to a remote server”.

Which basically means, gaining access to an information system or a website without logging in, as the user that the cookie (or session) belongs to him.

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Send Email on ESP8266 with Arduino

Arduino, ESP8266, PHP

Sending an email is probably the most convenient way of communicating data or informing us of an event from our ESP8266. It’s cross-platform, works on every device and very reliable. It can alert us when one of the sensors detected something (PIR sensor for movement, MQ2 for air quality or any other environmental sensor).
There are a few ways to get that done, and in this post, I’ll show you my preferable way.

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