Hello
im writing an inventory application for a customer that needs to calculate
item cost by Moving Average method which requires calculating the cost after
each operation, i have a good experience with TSQL but so far i failed to
write the statement that can do this WITHOUT writing cursors
im trying to avoid calculating cost after each transaction to the inventory
. and by writing a stored procedure , get a list showing transactions and
item avg in a period
here is a description of moving avg method , also available here for those
who cant read html
http://www.fms.indiana.edu/auxiliary/inventory.asp
Moving Average--Perpetual
Continuous or moving average assigns a unit value to cost of goods available
for sale. In this scenario, the average cost determines cost of goods sold
at the time of each sale. This method requires a calculation of average unit
cost after each purchase as illustrated below.
# of Units Cost per Unit Total Cost Moving Avg. Cost
Beginning inventory, 7/1 200
$5,000
$25.00
Purchase, 8/10 100
$26.00
2,600
Inv. Balance 300
7,600
25.33
Sale, 9/15 (100)
25.33
(2,533)
Inv. Balance 200
5,067
Purchase, 12/7 600
27.00
16,200
Inv. Balance 800
21,267
26.58
Sale, 12/18 (300)
26.58
(7,975)
Inv. Balance 500
13,292
Sale, 2/22 (250)
26.58
(6,645
Inv. Balance 250
6,647
Purchase, 3/20 300
28.00
8,400
Inv. Balance 550
15,047
27.36
Sale, 5/15 (150)
27.36
(4,104)
Inv. Balance 400
27.36
10,943
Ending Inventory 400
10,943
Cost of Goods Sold 100
2,533
300
7,975
250
6,645
150
4,104
800
$21,257
Regards
Bassamcan you post DDL and some data..and also the example..pasted correctly..
Av.
http://dotnetjunkies.com/WebLog/avnrao
http://www28.brinkster.com/avdotnet
"Bassam" <egbas@.yahoo.com> wrote in message
news:ORrEOZODFHA.3596@.TK2MSFTNGP12.phx.gbl...
> Hello
> im writing an inventory application for a customer that needs to calculate
> item cost by Moving Average method which requires calculating the cost
after
> each operation, i have a good experience with TSQL but so far i failed to
> write the statement that can do this WITHOUT writing cursors
> im trying to avoid calculating cost after each transaction to the
inventory
> . and by writing a stored procedure , get a list showing transactions and
> item avg in a period
> here is a description of moving avg method , also available here for those
> who cant read html
> http://www.fms.indiana.edu/auxiliary/inventory.asp
> Moving Average--Perpetual
> Continuous or moving average assigns a unit value to cost of goods
available
> for sale. In this scenario, the average cost determines cost of goods sold
> at the time of each sale. This method requires a calculation of average
unit
> cost after each purchase as illustrated below.
> # of Units Cost per Unit Total Cost Moving Avg. Cost
> Beginning inventory, 7/1 200
> $5,000
> $25.00
> Purchase, 8/10 100
> $26.00
> 2,600
>
> Inv. Balance 300
> 7,600
> 25.33
> Sale, 9/15 (100)
> 25.33
> (2,533)
>
> Inv. Balance 200
> 5,067
>
> Purchase, 12/7 600
> 27.00
> 16,200
>
> Inv. Balance 800
> 21,267
> 26.58
> Sale, 12/18 (300)
> 26.58
> (7,975)
>
> Inv. Balance 500
> 13,292
>
> Sale, 2/22 (250)
> 26.58
> (6,645
>
> Inv. Balance 250
> 6,647
>
> Purchase, 3/20 300
> 28.00
> 8,400
>
> Inv. Balance 550
> 15,047
> 27.36
> Sale, 5/15 (150)
> 27.36
> (4,104)
>
> Inv. Balance 400
> 27.36
> 10,943
>
> Ending Inventory 400
> 10,943
>
> Cost of Goods Sold 100
> 2,533
>
> 300
> 7,975
>
> 250
> 6,645
>
> 150
> 4,104
>
> 800
> $21,257
>
>
> Regards
> Bassam
>|||Please post DDL and some INSERT statements of your sample data:
http://www.aspfaq.com/etiquette.asp?id=5006
--
David Portas
SQL Server MVP
--|||On Mon, 7 Feb 2005 09:27:19 +0200, Bassam wrote:
>im writing an inventory application for a customer that needs to calculate
>item cost by Moving Average method which requires calculating the cost afte
r
>each operation, i have a good experience with TSQL but so far i failed to
>write the statement that can do this WITHOUT writing cursors
Hi Bassam,
I think you can get the moving average by a simple self-join with group
by. Check the following example:
-- First, create a table to hold all transactions
-- Opening balance is considered a transaction in this simplified example
CREATE TABLE Operations
(OpDate smalldatetime not null primary key,
Amount int not null, -- >0 purchase <0 sale
UnitPrice money not null)
go
-- Insert all data (same as on web page you mentioned)
INSERT Operations (OpDate, Amount, UnitPrice)
SELECT '20040701', 200, 25
UNION ALL
SELECT '20040810', 100, 26
UNION ALL
SELECT '20040915', -100, 25.33
UNION ALL
SELECT '20041207', 600, 27
UNION ALL
SELECT '20041218', -300, 26.58
UNION ALL
SELECT '20050222', -250, 26.58
UNION ALL
SELECT '20050320', 300, 28
UNION ALL
SELECT '20050515', -150, 27.36
go
-- Here's the statement that will calculate amount, value and moving
-- average after each of the transaction.
SELECT a.OpDate AS InvDate,
SUM(b.Amount) AS Amount,
SUM(b.Amount * b.UnitPrice) AS Value,
SUM(b.Amount * b.UnitPrice) / SUM(b.Amount) AS MovingAvg
FROM Operations AS a
INNER JOIN Operations AS b
ON b.OpDate <= a.OpDate
GROUP BY a.OpDate
ORDER BY a.OpDate
go
-- Done. Now clean up the mess.
DROP TABLE Operations
go
Best, Hugo
--
(Remove _NO_ and _SPAM_ to get my e-mail address)|||Hello Hugo,
Thank you for your input but result of your statement will calculate
"Weighted Average" not "Moving Average"
difference is shown in examples in this link
http://www.fms.indiana.edu/auxiliary/inventory.asp
if you open this page and search for weighted average you fill find the
example which works with your statement but the just below example which is
for moving average won't work
i will post DDL and some data here to clear the case
Regards
Bassam
"Hugo Kornelis" <hugo@.pe_NO_rFact.in_SPAM_fo> wrote in message
news:hhme01diqfdiohvb2rj3t896k5deoc47e9@.
4ax.com...
> On Mon, 7 Feb 2005 09:27:19 +0200, Bassam wrote:
>
calculate
after
> Hi Bassam,
> I think you can get the moving average by a simple self-join with group
> by. Check the following example:
> -- First, create a table to hold all transactions
> -- Opening balance is considered a transaction in this simplified example
> CREATE TABLE Operations
> (OpDate smalldatetime not null primary key,
> Amount int not null, -- >0 purchase <0 sale
> UnitPrice money not null)
> go
> -- Insert all data (same as on web page you mentioned)
> INSERT Operations (OpDate, Amount, UnitPrice)
> SELECT '20040701', 200, 25
> UNION ALL
> SELECT '20040810', 100, 26
> UNION ALL
> SELECT '20040915', -100, 25.33
> UNION ALL
> SELECT '20041207', 600, 27
> UNION ALL
> SELECT '20041218', -300, 26.58
> UNION ALL
> SELECT '20050222', -250, 26.58
> UNION ALL
> SELECT '20050320', 300, 28
> UNION ALL
> SELECT '20050515', -150, 27.36
> go
> -- Here's the statement that will calculate amount, value and moving
> -- average after each of the transaction.
> SELECT a.OpDate AS InvDate,
> SUM(b.Amount) AS Amount,
> SUM(b.Amount * b.UnitPrice) AS Value,
> SUM(b.Amount * b.UnitPrice) / SUM(b.Amount) AS MovingAvg
> FROM Operations AS a
> INNER JOIN Operations AS b
> ON b.OpDate <= a.OpDate
> GROUP BY a.OpDate
> ORDER BY a.OpDate
> go
> -- Done. Now clean up the mess.
> DROP TABLE Operations
> go
> Best, Hugo
> --
> (Remove _NO_ and _SPAM_ to get my e-mail address)|||On Mon, 7 Feb 2005 14:32:20 +0200, Bassam wrote:
>Hello Hugo,
>Thank you for your input but result of your statement will calculate
>"Weighted Average" not "Moving Average"
>difference is shown in examples in this link
>http://www.fms.indiana.edu/auxiliary/inventory.asp
>if you open this page and search for weighted average you fill find the
>example which works with your statement but the just below example which is
>for moving average won't work
Hi Bassam,
I did check that page, and the results of my query were equal to the
moving average quoted on that page (the table directly after the heading
"Moving Average--Perpetual").
>i will post DDL and some data here to clear the case
Excellent idea!
Best, Hugo
--
(Remove _NO_ and _SPAM_ to get my e-mail address)|||Hello Hugo,
I tested your statement, great , it works to a great detail !! , i found a
problem in the moving avg in date 2/22/05 , it should be exactly as the one
done on 12/18/04 (sales also) to be 26.5860 , but the one on 2/22/05 is
26.5920 (it is exactly 26.5860 in table) so i will make my tests what if i
put 20 sales transactions and see the result
but your statement gave max accurate to date to table.do you know a way to
overcome this small shift ?
thank you and welcome to any comments
Bassam|||On Mon, 7 Feb 2005 15:24:41 +0200, Bassam wrote:
>Hello Hugo,
>I tested your statement, great , it works to a great detail !! , i found a
>problem in the moving avg in date 2/22/05 , it should be exactly as the one
>done on 12/18/04 (sales also) to be 26.5860 , but the one on 2/22/05 is
>26.5920 (it is exactly 26.5860 in table) so i will make my tests what if i
>put 20 sales transactions and see the result
Hi Bassam,
I noted the difference as well. This is caused by rounding errors.
Consider the first few rows in the sample data. The beginning inventory
shows 200 units at a total cost of $ 5,000 - exactle $ 25.00 on average.
After the first purchase, there are 300 units on stock and the total cost
is equal to $ 7,600. The average price is $ 25.333333333333333 (etc), but
it is rounded down to $ 25.33. This would mean that if the following sale
would not be for 100 units (as listed in the example), but for 300 units,
the total sale price would be $ 7,599 and the remaining stock would be 0
units, for a total price of $ 1.
The example on the web page graciously avoids this anomaly by only
including a new price after each purchase. It doesn't list the moving avg
cost after a sale, so I could not verify if the values given by my query
are correct or not.
If you need the moving average cost to reflect the situation after the
last purchase instead of after the last sale, try this (slightly more
complicated) query:
SELECT a.OpDate AS InvDate,
SUM(b.Amount) AS Amount,
SUM(b.Amount * b.UnitPrice) AS Value,
(SELECT SUM(c.Amount * c.UnitPrice) / SUM(c.Amount)
FROM Operations AS c
WHERE c.OpDate <= (SELECT MAX(d.OpDate)
FROM Operations AS d
WHERE d.OpDate <= a.OpDate
AND d.Amount > 0)) AS MovingAvg
FROM Operations AS a
INNER JOIN Operations AS b
ON b.OpDate <= a.OpDate
GROUP BY a.OpDate
ORDER BY a.OpDate
(Note: if you only need the date and the moving average, not the amount
and value of the inventory, you can remove the group by and the join to
"Operations AS b" - IOW, you can simplify to:
SELECT a.OpDate AS InvDate,
(SELECT SUM(c.Amount * c.UnitPrice) / SUM(c.Amount)
FROM Operations AS c
WHERE c.OpDate <= (SELECT MAX(d.OpDate)
FROM Operations AS d
WHERE d.OpDate <= a.OpDate
AND d.Amount > 0)) AS MovingAvg
FROM Operations AS a
ORDER BY a.OpDate
Best, Hugo
--
(Remove _NO_ and _SPAM_ to get my e-mail address)|||Bassam,
Thanks to Hugo for posting the DDL for the table, I will assume it is
correct. Here is a try, but do not compare to the table in the link, there i
s
an error there.
Error in the link:
Sale, 12/18 (300) 26.58 (7,975)
well, -300 * 26.58 should be 7,974.
select
a.OpDate,
sum(b.Amount) as number_of_units,
sum(b.Amount * b.UnitPrice) as total_cost,
(
select
sum(c.Amount * c.UnitPrice) / sum(c.Amount)
from
Operations as c
where
c.OpDate <= (
select
max(d.OpDate)
from
Operations as d
where
sign(d.Amount) >= 0 and d.OpDate <= a.OpDate
)
) as moving_avg_cost
from
Operations as a
inner join
Operations as b
on a.OpDate >= b.OpDate
group by
a.OpDate
order by
a.OpDate
go
AMB
"Bassam" wrote:
> Hello Hugo,
> Thank you for your input but result of your statement will calculate
> "Weighted Average" not "Moving Average"
> difference is shown in examples in this link
> http://www.fms.indiana.edu/auxiliary/inventory.asp
> if you open this page and search for weighted average you fill find the
> example which works with your statement but the just below example which i
s
> for moving average won't work
> i will post DDL and some data here to clear the case
> Regards
> Bassam
>
> "Hugo Kornelis" <hugo@.pe_NO_rFact.in_SPAM_fo> wrote in message
> news:hhme01diqfdiohvb2rj3t896k5deoc47e9@.
4ax.com...
> calculate
> after
>
>|||Hello Hugo,
Thank you, Clear and efficient ! , only last problem , what if a user need
to delete a purchasing happened at beginning of month - or adjust its unit
price value, that means all next averages used in next sales is wrong and
need to be recalculated, is there a way to recalculate unit price for sales
transactions ' i need to adjust that before using your statement again or
result will be wrong
to make situation more complicated is that it might also be more purchasing
down there with sales, i mean suppose user deleted 1 of 5 purchasing done at
beginning of the month , on day 1 , while other purchasing happened on day 5
, 8 , 12 , 14 remains , and there are sales in between. , how then i can
recalculate unit price (which is the moving average) for sales
transactions.in between ?
Thank you
Bassam
