does the order of columns in a SQL select matters?

Question

my question is regarding a left join I've tried to count how many people are tracking a certain project. (there can be zero followers)

now the only way i can get it to work is by adding

group by idproject

my question is if the is a way to avoid using this and only selecting and implicitly
setting that group option.

SQL:

select `project_view`.`idproject` AS `idproject`,
count(`track`.`iduser`) AS `c`,`name`
from `project_view` left join `track` using(idproject)

I expected it count null as zero but it doesn't appear at all,
if i neglect counting then it shows as null where there are no followers.

Answer 1

If you have a WHERE clause to specify a certain project then you don't need a GROUP BY.

SELECT project_view.idproject, COUNT(track.iduser) AS c, name
FROM project_view
LEFT JOIN track USING (idproject)
WHERE idproject = 4

If you want a count for each project then you do need a GROUP BY.

SELECT project_view.idproject, COUNT(track.iduser) AS c, name
FROM project_view
LEFT JOIN track USING (idproject)
GROUP BY idproject

Answer 2

Yes the order of selecting matters. For performance reasons you (typically) want your most limiting select first to narrow your data set. This makes every subsequent query operate on a smaller dataset.