What causes Duplicated Queries and how do I prevent it?

[fkisserh]

Anytime I enable debug mode in global configuration, I see a duplicated queries section under
Database Queries Tab as shown in the attached image

JoomlaScreenshot.png

.

I will like to know :

Are these normal?
Does every Joomla site have them?
Can I get rid of them?
How do I prevent these duplicated queries?

I see this on every single Joomla Site I have created in the last 5 years. Even on freshly installed sites without any extensions. Are they deliberate?

[simplesource]

The debug plugin is cloning the session data when building an output for each page, which requires re-initializing any stored information including a user's serialized JUser object. I would just ignore it and move on.

[SharkyKZ]

You can click on "Call Stack" next to each query to find out exactly where it's coming from.
It's normal to have some duplicate queries in backend and a few in frontend. It really depends on exact page, enabled plugins and modules, their options.
Duplicate queries can generally be reduced by improving the code. Not in all cases though. Without making code changes, you can enable cache, remove or disable unneeded extensions.