А можно сделать 3 GROUP BY один в другом. То есть надо объединить 3 запроса в один, а как не знаю
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-- ПЕРВЫЙ
select
history.ghacct,
convert(varchar(10),information.info),
convert(varchar(8),(select info from information where code='TYPE' and information.account=history.ghacct)),
history.name,
history.sex,
convert(varchar(10),history.dob, 103),
history.zip,
history.country,
history.city,
history.address,
history.state,
transactions.tran_code, sum(transactions.amount)
from
information, history, guest , transactions, z_trancode
where information.code='N' and
information.account=history.ghacct and
history.ghacct=guest.ghacct and
guest.account=transactions.account and
transactions.tran_code=z_trancode.code and
z_trancode.trantype in ('200', 'RV','FB')
group by history.ghacct, information.info, history.name, history.sex, history.dob, history.zip, history.country,
history.city, history.address, history.state, transactions.tran_code

--ВТОРОЙ
select sum(transactions.amount), transactions.tran_code, history.ghacct
from transactions, z_trancode, information, history, guest
where
information.code='N' and
information.account=history.ghacct and
history.ghacct=guest.ghacct and
guest.account=transactions.account and
transactions.tran_code=z_trancode.code and
z_trancode.trantype in ('200', 'RV','FB') and
transactions.tran_code in ('206', '300', '215', '220', '999')
group by transactions.tran_code, history.ghacct

--ТРЕТИЙ
select sum(transactions.amount), history.ghacct
from transactions, z_trancode, information, history, guest
where
information.code='N' and
information.account=history.ghacct and
history.ghacct=guest.ghacct and
guest.account=transactions.account and
transactions.tran_code=z_trancode.code and
z_trancode.trantype in ('200', 'RV','FB') and
transactions.tran_code not in ('206', '300', '215', '220', '999')
group by history.ghacct

Пробовал, пишет:

Server: Msg 205, Level 16, State 1, Line 6
All queries in an SQL statement containing a UNION operator must have an equal number of expressions in their target lists.