session_id (int 11)
cpa (int 11)
revenue (int 11)

call_session_id (int 11)
agent (int 5)

agent sum(cpa)
17     200

SELECT s.agent, SUM(c.cpa)
FROM edu.conversions c JOIN edu.cc_sessions s ON c.session_id = s.call_session_id
WHERE c.revenue = '0' AND c.cpa > '0'

SELECT s.agent, SUM(c.cpa)
FROM edu.conversions c
JOIN edu.cc_sessions s ON c.session_id = s.call_session_id
WHERE c.revenue = '0'
AND c.cpa > '0'
GROUP BY s.agent

SELECT s.agent, SUM(c.cpa)
FROM edu.conversions c
JOIN edu.cc_sessions s ON c.session_id = s.call_session_id
WHERE c.revenue = 0
AND c.cpa > 0
GROUP BY s.agent

SELECT s.agent, SUM(c.cpa)
FROM conversion c JOIN cc_sessions s ON s.call_session_id = c.session_id
WHERE c.revenue = 0 AND c.cpa > 0
GROUP BY s.agent;