Author Archives: technote

[Database / mysql] Understanding ‘on delete cascade’

As I was studying the database, I came up with the syntax ‘on delete cascade’. When a tuple is deleted, the tuple associated with the foreign key is deleted as well. But there was a part that was not clearly understood.   If we delete the tuple of relation A, does tuple of relation B… Read More »

Linux – iconv – Change File Encoding

When parsing HTML, the HTML(korean site) may be euc-kr or utf-8. Personally, I usually work on a linux terminal, but the linux terminal is usually utf-8. So, if I check the contents of the html file encoed by eucKR in this environment, I can see that Hangul(korean character) is broken. [If euc-kr  encoded file is… Read More »

Python – Execution of Code

One of the first things you need to do when you learn python is how to run the python code you wrote. The most important thing when you learn a language is to try it yourself and see the results with your eyes. There are several ways to execute code written in python. 1. Running… Read More »

Python – Boolean / Bitwise operation

The logical operator and the bitwise operator are similar to each other, so the difference makes me confused. What is the difference between the logical operator “and” and the bitwise operator “&”? What is the difference between the logical operator “or” and the bitwise operator “|”? What is the difference between the logical operator “not”… Read More »

Comparison of Github and Gitlab.

Source code management is very important when developers are developing. For example, after implementing basic functions and copying one backup, implementing additional functions, copying one backup, doing code management like this, I do not remember what purpose I copied, I am also trying to compare the current code with the current one. Therefore, in order… Read More »

The unit of the RF signal. dB and dBm

When you are viewing RF-related documentation or logs, you often see a unit called dB and dBm. In fact, I did not use them differently until now. But I find that there are different meanings. Received Signal Strength Indicator: -49dBm The above shows the signal strength of Wi-Fi as part of the log when you… Read More »