Parece que esto es lo que quieres. Actualicé la primera consulta para usar ANSI JOIN adecuado sintaxis y luego para las dos consultas adicionales se unieron a través de LEFT JOIN en el stats_host campo:
SELECT s.stats_host,
h.host_name,
s.stats_avgcpu,
s.stats_avgmem,
s.stats_avgswap,
s.stats_avgiowait,
s7.7dayavgcpu,
s7.7dayavgmem,
s7.7dayavgswap,
s7.7dayavgiowait,
s30.30dayavgcpu,
s30.30dayavgmem,
s30.30dayavgswap,
s30.30dayavgiowait
FROM sar_stats s
INNER JOIN sar_hosts h
on s.stats_host = h.host_id
INNER JOIN sar_appgroups a
on h.host_appgroup = a.group_id
and a.group_name = 'Pervasive'
INNER JOIN sar_environments e
on h.host_environment = e.env_id
and e.env_name = 'Staging 2'
LEFT JOIN
(
SELECT s.stats_host,
AVG(s.stats_avgcpu) AS '7dayavgcpu',
AVG(s.stats_avgmem) AS '7dayavgmem',
AVG(s.stats_avgswap) AS '7dayavgswap',
AVG(s.stats_avgiowait) AS '7dayavgiowait'
FROM sar_stats s
WHERE DATE(stats_report_time) BETWEEN DATE_SUB(curdate(), INTERVAL 8 DAY) AND DATE_SUB(curdate(), INTERVAL 1 DAY)
GROUP BY s.stats_host
) s7
on s.stats_host = s7.stats_host
LEFT JOIN
(
SELECT s.stats_host,
AVG(s.stats_avgcpu) AS '30dayavgcpu',
AVG(s.stats_avgmem) AS '30dayavgmem',
AVG(s.stats_avgswap) AS '30dayavgswap',
AVG(s.stats_avgiowait) AS '30dayavgiowait'
FROM sar_stats s
WHERE DATE(s.stats_report_time) BETWEEN DATE_SUB(curdate(), INTERVAL 31 DAY) AND DATE_SUB(curdate(), INTERVAL 1 DAY)
GROUP BY s.stats_host
) s30
on s.stats_host = s30.stats_host
WHERE DATE(s.stats_report_time) = DATE_SUB(curdate(), INTERVAL 1 DAY);
