sql - Different between mySQL queries INNER JOIN -

this question has answer here:

• inner join on vs clause 10 answers

i have 2 queries:

$query = mysql_query("select ord.orderid, customers.customername,                              ord, customers                       customers.customersalary=ord.orderid"); 

and

$query = mysql_query("select ord.orderid, customers.customername,                        ord                       inner join customers                       on customers.customersalary=ord.orderid"); 

this queries return same result. different between them.

$query = mysql_query("select ord.orderid, customers.customername,                        ord                       inner join customers                       on customers.customersalary=ord.orderid"); 

this query optimised other 1 inner join applied first , clause applied.

other benifit see can change inner outer join.

clean code.