SQL 2012 :: Queries Based On ER Diagram And Joining Tables

I need to create a few select queries based on an er diagram.

These are my Create Table statements and import statements:

Create Table Agent (Aid integer primary key, Pid integer, aName text);
Create Table Product (Pid integer primary key, pName text);
Create Table Supplier (Sid integer primary key, sName text);
Create table Supplies (Sid integer, Pid integer, price decimal(8,2));

.import agent.txt Agent
.import product.txt Product
.import supplier.txt Supplier
.import supplies.txt Supplies

I think I got all my create table statements are correct.

I need to Find the number of agents for each supplier that has at least one agent. The result should be tuples of the form (sid, sName, number of agents)

-Select Sid, sName, count(Aid) from Agent A join Supplier S on (S.Sid = A.Sid) group by S.Sid, S.sName, Aid;
But it gives me this error: no such column: A.Sid

Im thinking I might have a problem with my create table statement and/or primary key statements?