[SQL] One-2-many relation - need distinct counts

[PS PS]

Hi gurus,

I have table A, B and need a distinct count of
Accounts from A.  There is a one-2-many relation
between A and B.  Accounts # in A are all unique. 
However, in B there will be duplicates.  So the
problem I have is, when I join as follows:
Select Count(Distinct(account_no)) 
from A, B 
where A.Account_no = B.Account_no

I get the correct count.  If I do this:
Select Count(Distinct(account_no)), B.Account_type 
from A, B 
where A.Account_no = B.Account_no 
group by B.Account_type

I get wrong counts because there some are duplicated. 
I tried everything that I can think of - subquery, sub
table etc.  I would appreciate some help in writing
the query.  Thanks in advance.

PS

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[SQL] Max Columns in a SQL Select

[PS PS]

SQL Guru's,

Does anyone know what is the Column Limit in a SQL
Query in Oracle RDB version 7.1?  

I've about 200 columns in my SQL query.  Each column
is a computed column -- Case when a = b Then c Else 0
End.

It gives me a runtime error -- abnormal program
termination -- upon execution.  

Thanks a lot in advance.




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