Problema con Consulta en SQL

[Libras]

Código SQL:

SELECT alias.SKILL,
SUM(alias.t_hold+alias.t_talk)/ SUM(alias.n_inb) AS TMO
FROM 
(
SELECT 'UNIMARC' AS SKILL, 
t_hold,
t_talk,
n_inb,
time_key 
FROM R_GA_UNIM_DAY 
UNION
SELECT 'MASISA' AS SKILL,
t_hold,
t_talk,
n_inb,
time_key 
FROM R_MASISA_DAY
UNION
SELECT 'BANCO' AS SKILL,
t_hold,
t_talk,
n_inb,
time_key 
FROM R_GA_BFA_DAY BF
UNION
SELECT 'SECURITY' AS SKILL,
t_hold,
t_talk,
n_inb,
time_key 
FROM R_SECUCO_DAY 
UNION
SELECT 'SECURITY' AS SKILL,
t_hold,
t_talk,
n_inb,
time_key 
FROM R_SECUPC_DAY
) AS alias
WHERE alias.time_key BETWEEN ('20150629') AND ('20150705')
GROUP BY alias.SKILL