Question

while trying to learn sql i came across “Learn SQL The Hard Way” and i started reading it.
Everything was going fine then i thought ,as a way to practice, to make something like given example in the book (example consists in 3 tables pet,person,person_pet and the person_pet table ‘links’ pets to their owners).

I made this:

report table
+----+-------------+
| id | content     |
+----+-------------+
|  1 | bank robbery|
|  2 | invalid     |
|  3 | cat on tree |
+----+-------------+
notes table
+-----------+--------------------+
| report_id | content            |
+-----------+--------------------+
|  1        | they had guns      |
|  3        | cat was saved      |
+-----------+--------------------+

wanted result
+-----------+--------------------+---------------+
| report_id | report_content     | report_notes  |
+-----------+--------------------+---------------+
|  1        | bank robbery       | they had guns |
|  2        | invalid            | null or ''    |
|  3        | cat on tree        | cat was saved |
+-----------+--------------------+---------------+

I tried a few combinations but no success.

My first thought was

SELECT report.id,report.content AS report_content,note.content AS note_content
FROM report,note
WHERE report.id = note.report_id

but this only returns the ones that have a match (would not return the invalid report).
after this i tried adding IF conditions but i just made it worse.

My question is, is this something i will figure out after getting past basic sql
or can this be done in simple way?

Anyway i would appreciate any help, i pretty much lost with this.

Thank you.

EDIT: i have looked into related questions but havent yet found one that solves my problem.
I probably need to look into other statements such as join or something to sort this out.

Answer 1

You need to get to the chapter on OUTER JOINS, specifically, a LEFT JOIN

SELECT report.id,report.content AS report_content,note.content AS note_content 
FROM report
    LEFT JOIN note ON report.id = note.report_id 

Note the ANSI-92 JOIN syntax as opposed to using WHERE x=y

(You can probably do it using the older syntax you were using WHERE report.id *= note.report_id, if I recall the old syntax correctly, but I’d recommend the above syntax instead)