SQL looping Cartesian Product

Question

I have limited experience with SQL and I am currently working on a small project to create a view from different tables. However I keep getting a cartesian product in the result.

I have 3 tables that I am working with, first table has information on each branch, second table has account numbers and names and the third table has monthly totals. I want to create a view where each row has the account numbers followed by a column for each month.

ACCT Table - Number (Primary Key), Acct Number, Account Name and bunch of other columns that are not important for this project.

TOTAL Table - Branch Number (points to BRANCH table), Month (MM-YYYY format), Acct Number (Points to the primary key of the ACCT table) and the monthly totals column.

Acct - Acct Name - Jan Amount - Feb Amount - Mar Amount .....Dec Amount

I wanted to do something like a for-each loop (for each acct, show the monthly totals) but since SQL doesn't have that option I did the following. I am not even joining the branch table at this point and with only 2 months selected I am getting a cartesian product.

select a.scode glacct, a.sdesc glacctdescp,
t1.smtd Amt01, t2.smtd Amt02
from acct a
inner join total t1 on a.hmy = t1.hacct and t1.umonth = '2013-01-01' and t1.ibook = '1'
left outer join total t2 on a.hmy = t2.hacct and t2.umonth = '2013-02-01' and t2.ibook = '1'

I would appreciate it if you can tell me how to fix the inner join statements since that is where I have the problem. Individually it gives me the information I am looking for but joins are not working.

Thanks

Answer 1

in mysql, if you want total by month, this should look like that

select a.scode glacct, a.sdesc glacctdescp
sum(case when month(t.umonth) = 1 then t.smtd else 0 end) as JanuaryAmount,
sum(case when month(t.umonth) = 2 then t.smtd else 0 end)as FebruaryAmount,
sum(case when month(t.umonth) = 3 then t.smtd else 0 end) as MarchAmount
--etc.
from acct a
inner join total t on a.hmy = t.hacct
where year(t.umonth)=2013
and t.ibook = 1
group by a.scode, a.sdesc

Answer 2

The answer from Raphael is probably pretty close, The big reason for your Cartesian product is that you are not grouping and summing the detail lines, which I think is your goal. Another way to approach it would be to simply group by the Year, Month and Account so you would get a result line for each account each month of each year in the data set.

select a.scode glacct, a.sdesc glacctdescp,
sum(t1.smtd)
from acct a
inner join total t1 on a.hmy = t1.hacct and t1.umonth = '2013-01-01' and t1.ibook = '1'
left outer join total t2 on a.hmy = t2.hacct and t2.umonth = '2013-02-01' and t2.ibook = '1'
Group by Year(t1.umonth), Month(t1.umonth),glacct,a.scode