SELECT * 
FROM moritz.agents;

SELECT * 
FROM moritz.services;

SELECT * 
FROM moritz.agents, moritz.services;

SELECT agents.id as agent, agents.id_service as id_service, services.id service 
FROM moritz.agents, moritz.services;

SELECT agents.id as agent, agents.id_service as id_service, services.id service 
FROM moritz.agents, moritz.services 
WHERE agents.id_service=services.id;

SELECT agents.id as agent, agents.id_service as id_service, services.id service 
FROM moritz.agents, moritz.services 
WHERE agents.id_service=services.id AND services.id=2;

SELECT agents.id as agent, agents.id_service as id_service, services.id service 
FROM moritz.agents JOIN moritz.services ON (agents.id_service=services.id)
WHERE services.id=2;