Include missing years in Group By query - sql

Question

I am fairly new in Access and SQL programming. I am trying to do the following:
Sum(SO_SalesOrderPaymentHistoryLineT.Amount) AS [Sum Of PaymentPerYear]
and group by year even when there is no amount in some of the years. I would like to have these years listed as well for a report with charts. I'm not certain if this is possible, but every bit of help is appreciated.
My code so far is as follows:
SELECT
Base_CustomerT.SalesRep,
SO_SalesOrderT.CustomerId,
Base_CustomerT.Customer,
SO_SalesOrderPaymentHistoryLineT.DatePaid,
Sum(SO_SalesOrderPaymentHistoryLineT.Amount) AS [Sum Of PaymentPerYear]
FROM
Base_CustomerT
INNER JOIN (
SO_SalesOrderPaymentHistoryLineT
INNER JOIN SO_SalesOrderT
ON SO_SalesOrderPaymentHistoryLineT.SalesOrderId = SO_SalesOrderT.SalesOrderId
) ON Base_CustomerT.CustomerId = SO_SalesOrderT.CustomerId
GROUP BY
Base_CustomerT.SalesRep,
SO_SalesOrderT.CustomerId,
Base_CustomerT.Customer,
SO_SalesOrderPaymentHistoryLineT.DatePaid,
SO_SalesOrderPaymentHistoryLineT.PaymentType,
Base_CustomerT.IsActive
HAVING
(((SO_SalesOrderPaymentHistoryLineT.PaymentType)=1)
AND ((Base_CustomerT.IsActive)=Yes))
ORDER BY
Base_CustomerT.SalesRep,
Base_CustomerT.Customer;

Answer 1

You need another table with all years listed -- you can create this on the fly or have one in the db... join from that. So if you had a table called alltheyears with a column called y that just listed the years then you could use code like this:
WITH minmax as
(
select min(year(SO_SalesOrderPaymentHistoryLineT.DatePaid) as minyear,
max(year(SO_SalesOrderPaymentHistoryLineT.DatePaid) as maxyear)
from SalesOrderPaymentHistoryLineT
), yearsused as
(
select y
from alltheyears, minmax
where alltheyears.y >= minyear and alltheyears.y <= maxyear
)
select *
from yearsused
join ( -- your query above goes here! -- ) T
ON year(T.SO_SalesOrderPaymentHistoryLineT.DatePaid) = yearsused.y

Answer 2

You need a data source that will provide the year numbers. You cannot manufacture them out of thin air. Supposing you had a table Interesting_year with a single column year, populated, say, with every distinct integer between 2000 and 2050, you could do something like this:
SELECT
base.SalesRep,
base.CustomerId,
base.Customer,
base.year,
Sum(NZ(data.Amount)) AS [Sum Of PaymentPerYear]
FROM
(SELECT * FROM Base_CustomerT INNER JOIN Year) AS base
LEFT JOIN
(SELECT * FROM
SO_SalesOrderT
INNER JOIN SO_SalesOrderPaymentHistoryLineT
ON (SO_SalesOrderPaymentHistoryLineT.SalesOrderId = SO_SalesOrderT.SalesOrderId)
) AS data
ON ((base.CustomerId = data.CustomerId)
AND (base.year = Year(data.DatePaid))),
WHERE
(data.PaymentType = 1)
AND (base.IsActive = Yes)
AND (base.year BETWEEN
(SELECT Min(year(DatePaid) FROM SO_SalesOrderPaymentHistoryLineT)
AND (SELECT Max(year(DatePaid) FROM SO_SalesOrderPaymentHistoryLineT))
GROUP BY
base.SalesRep,
base.CustomerId,
base.Customer,
base.year,
ORDER BY
base.SalesRep,
base.Customer;
Note the following:
The revised query first forms the Cartesian product of BaseCustomerT with Interesting_year in order to have base customer data associated with each year (this is sometimes called a CROSS JOIN, but it's the same thing as an INNER JOIN with no join predicate, which is what Access requires)
In order to have result rows for years with no payments, you must perform an outer join (in this case a LEFT JOIN). Where a (base customer, year) combination has no associated orders, the rest of the columns of the join result will be NULL.
I'm selecting the CustomerId from Base_CustomerT because you would sometimes get a NULL if you selected from SO_SalesOrderT as in the starting query
I'm using the Access Nz() function to convert NULL payment amounts to 0 (from rows corresponding to years with no payments)
I converted your HAVING clause to a WHERE clause. That's semantically equivalent in this particular case, and it will be more efficient because the WHERE filter is applied before groups are formed, and because it allows some columns to be omitted from the GROUP BY clause.
Following Hogan's example, I filter out data for years outside the overall range covered by your data. Alternatively, you could achieve the same effect without that filter condition and its subqueries by ensuring that table Intersting_year contains only the year numbers for which you want results.
Update: modified the query to a different, but logically equivalent "something like this" that I hope Access will like better. Aside from adding a bunch of parentheses, the main difference is making both the left and the right operand of the LEFT JOIN into a subquery. That's consistent with the consensus recommendation for resolving Access "ambiguous outer join" errors.

Answer 3

Thank you John for your help. I found a solution which works for me. It looks quiet different but I learned a lot out of it. If you are interested here is how it looks now.
SELECT DISTINCTROW
Base_Customer_RevenueYearQ.SalesRep,
Base_Customer_RevenueYearQ.CustomerId,
Base_Customer_RevenueYearQ.Customer,
Base_Customer_RevenueYearQ.RevenueYear,
CustomerPaymentPerYearQ.[Sum Of PaymentPerYear]
FROM
Base_Customer_RevenueYearQ
LEFT JOIN CustomerPaymentPerYearQ
ON (Base_Customer_RevenueYearQ.RevenueYear = CustomerPaymentPerYearQ.[RevenueYear])
AND (Base_Customer_RevenueYearQ.CustomerId = CustomerPaymentPerYearQ.CustomerId)
GROUP BY
Base_Customer_RevenueYearQ.SalesRep,
Base_Customer_RevenueYearQ.CustomerId,
Base_Customer_RevenueYearQ.Customer,
Base_Customer_RevenueYearQ.RevenueYear,
CustomerPaymentPerYearQ.[Sum Of PaymentPerYear]
;