I have seen code where the inner join is explicitly used, i also have seen code where the usage is just join.

select * from a
inner join b on a.id=b.id

or

select * from a
join b on a.id=b.id

Can anyone explain what are the differences between these two joins?
Thank you.

or from taba a,tabb b.. is the same
if not explicit always inner join

the keyword INNER is optional

however, it is always a good idea to write it anyway

same with LEFT JOIN -- the keyword OUTER is optional but i always write it