As stated before you can apply the JOINs in any order you wish, the outcome will be the same for all possible orders.
For all intents and purposes you can assume they will be executed from left to right, but this is not necessarily the case as the database will figure out the order itself for each individual query.
In other words
(A JOIN B) JOIN C produces the same result as A JOIN (B JOIN C)
provided you use the same join criteria, of course
- A, B, C can also be JOINs themselves; you can nest this as much as you like.
The only exception I can think of is if you calculate something from two tables and then use that result to join with a third table, in which case the tables that the calculation is based on need to be joined first; this is pretty exceptional though - I can't remember ever doing this and I've been writing queries for 10+ years.