SQL query to display data

It's not an exercise, it's a problem that I want solved.

This query does not work:

SELECT * FROM persons, structures WHERE workplace = structure_id AND assignment = structure_id

How can I solve the problem please?

@okbabbLook, for example, at how the left join works.

@jordane45You will also need to pay attention to the aliases... because you have to join your structures table twice (once for each link with your persons table).

@jordane45Thank you, but sorry, I don't quite understand the problem. Can you please correct the request?

MySQL DBMS and project on PHP,
I did some research on joins but it is more complicated than my simple task.

@okbabbComplicated ??
Yet, it seems pretty simple to understand to me.. https://sql.sh/cours/jointures/left-join
And a course on joins.. and aliases: https://joaomarcuraa.medium.com/sql-joins-and-aliases-1965fd2423ca

@jordane45Thank you, I read all of that, but I can't find my example.

@okbabbYou won't find an example that perfectly matches your needs... it's up to you to understand how it works and apply it...

Start with an initial join between your two tables, see what it gives you...
then, add a second join between your two tables... and there you go... job done...
In short

 SELECT * FROM table1 T1 LEFT JOIN table2 T2 ON T2.xx = T1.zz LEFT JOIN table2 T3 on T3.ww = T1.yy 

1 - Do not post images... but the code directly on the forum using the code tags!
2 - An SQL query should be tested FIRST directly in the database (using phpMyAdmin for example)
3 - You will need to add ALIASES as well in the "SELECT" part of your query to identify the fields (since you have the same ones multiple times..)

NB: Explanations regarding the use of code tags to read completely before returning:
https://codes-sources.commentcamarche.net/faq/11288-les-balises-de-code

.

And what is the error exactly? (because... giving us this information would greatly help in resolving it..)

@jordane45Isn't it a question of ambiguous ID in the order by ??
It should be prefixed by the alias of the table that concerns this field .. T1.id for example.

Oh, but you're talking about a PHP error message... who cares about that!
First of all, because your question concerns the construction of an SQL query, which is posted in the Database forum... and moreover, I told you to test your queries DIRECTLY in your database before wanting to use them in code.

Not to mention that your PHP code is outdated... but I'll talk to you about that later when you've finally made the query for which you asked us for help...

@jordane45For the aliases .. you clearly still haven't taken the time to read the links I gave you.
Everything is explained there ...
For example

 SELECT T1.id as ID1, T2.id as ID2 ... 

@jordane45error too

@jordane45The thing is very simple, but I don't know how to do it. Here is another example,

a table "users" that contains 4 columns: id, name, country_of_origin, country_of_residence

id name country_of_origin country_of_residence
1 michel 1 2
2 celine 3 4

and another table "countries" that contains 2 columns: country_id, country_name

country_id country_name
1 france
2 belgium
3 spain
4 switzerland

I want a final table like this: (output)

name country_of_origin country_of_residence
michel france belgium
celine spain switzerland

what is the SQL query? Thank you in advance.

@okbabbYou have an error because you did not use the table alias in the SELECT part...

 T1.location.... 

And not

 persons.location.... 

Unless you did not write the column name correctly? (but not knowing the exact structure of your database, it's hard for me to guess from a distance)