SQL Duplicate entry for key 1 - mysql

Question

I've recently had to take over the management of a database (within a school) that records certain stats, at the start of each year these stats are supposed to be reset.
I've been given a piece of code to run to reset these stats, however it is throwing out a 'Duplicate entry '10172-0' for key 1 error when I try to run it. (the '10172-0' part also happens on various other numbers/student_id's). The code I've been given is:
Insert into cfc.student_stats (students_id, no_cfcs)
Select student_id, 0
from roombookings.students
where student_id >= 1
and student_id <= 15635
I've checked and there aren't duplicate entries when I check out the various student_id's so I'm at a loss with what to do. Underneath the error message I get a button to 'Browse' which then tells me the following:
Error
SQL query: Documentation
SELECT *
FROM
WHERE CONCAT_WS( "-", students_id, no_cfcs ) = "10172-0"
ORDER BY students_id, no_cfcs
MySQL said: Documentation
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'WHERE CONCAT_WS("-", students_id, no_cfcs)
= "10172-0"' at line 3
I've had a browse through lots of other similar problems on here but none of them seemed to match up with what I was getting (but I don't really understand SQL). Any help appreciated, cheers!

Answer 1

You are doing this
SELECT *
FROM
WHERE
in above query you missed to add table name.
Edit
SELECT *
FROM
roombookings.students
WHERE

Answer 2

Regarding that second error, I'm not sure why you don't just use:
WHERE students_id = 10172 AND no_cfcs = 0
It seems a bit silly and inefficient to turn them into strings just to compare them.
In addition, it appears you haven't selected an actual table to read from, so something like this would be better:
SELECT *
FROM cfc.student_stats
WHERE students_id = 10172
AND no_cfcs = 0
There's also no point ordering by students_id, no_cfcs when you're only allowing one possibility for each, so I removed that bit.
Regarding your first error, I suspect that may be because of duplicate entries in the roombookings.students table. If you do:
select student_id, count(*)
from roombooking.students
where student_id >= 1 and student_id <= 15635
group by student_id
and the second column has any number greater than one in it, you'll get an error trying to insert duplicates into the cfc.student_stats table.
That's because for each student_id in that roombooking.students table, you'll try to create one in the cfc.student_stats table with a primary key made up of the student ID and the constant 0.
If you don't get any counts greater than one, then it's most likely that there's already a row in the cfc.student_stats table with that student ID.