Deciphering Views SQL I am trying to understand Views SQL, and am using a query of some Commerce data to increase my understanding.  Here is the start of a query:

SELECT commerce_order.order_id AS order_id, 
commerce_customer_profile_field_data_commerce_customer_billing.profile_id     
AS commerce_customer_profile_field_data_commerce_customer_billi, ...


The first part of this is straightforward enough, it is just picking up the order_id from the commerce_order table. The second item, though is puzzling: the first part, commerce_customer_profile is just a table, but then the second part field_data_commerce_custom_billing is another table, and the two are connected by an underscore. 

In other words, the construct looks like this: SELECT table1_table2.field. I have searched at length for an explanation of this syntax, but cannot find anything
how table aliases are created in joins is pretty simple - to have unique alias views takes names of both tables and combines them.
you can check more simple example:

SELECT node.created AS node_created, node.nid AS nid, users_node.mail AS users_node_mail
FROM 
{node} node
LEFT JOIN {users} users_node ON node.uid = users_node.uid


users table is joined to node table and unique name becomes "users_node". For files table it would files_node. 

I think it is the only way to have unique aliases. Also it is easy to understand from which join data is coming