Question: What is the name of the shipping agent of the document with id 2?
Schema: create table documents (id varchar, PRIMARY KEY (id)); create table ref_shipping_agents (id varchar, PRIMARY KEY (id))
SQL: select ref_shipping_agents.shipping_agent_name from ref_shipping_agents join documents on documents.shipping_agent_code = ref_shipping_agents.shipping_agent_code where documents.document_id = 2