leftjoin and multiple leftjoin execution order

Give a simple explanation. 
Example table a 
aid adate 
1 a1 
2     a2
 3     a3
 table b 
bid bdate 
1 b1 
2      b2
 4      b4
 two tables a, b are connected, to take out the field with the same id 
select * from a inner join b on a.aid = b.bid This is to take out only matching data. 
At this time, what is taken out is: 
1 a1 b1 
2 a2  b2
 Then left  join means: 
select * from a left  join b on a.aid = b.bid 
First Take out all the data in the a table, and then add the data that matches a and b. 
At this time, the taken out is: 
1 a1 b1 
2 a2  b2
 3 a3 null characters 
also have right join
It means to first take out all the data in the b table, and then add the data matching a and b. 
At this time, what is taken out is: 
1 a1 b1 
2 a2 b2 
4 null character b4

Original link: http://zhidao.baidu.com/link?url=hOCkB8JOoN-3n7_K9kc5QUNn7frEj6cmmvQi4tehTI2AUbCtQVY2tr023_SkOcvBpg6d72KYvktxxkzt3i9N4q

 Ask for advice on how to perform multiple left joins 
eg:
 select * from a left join b on a.abid = b.baid left join c on c.cbid = b.bcid The 
order is to first combine a and b into a virtual table, and then the virtual table And then associated with the C table