dimensional data modelling design - Data warehouse - olap

I am having
dimension tables
item (item_id,name,category)
Store(store_id,location,region,city)
Date(date_id,day,month,quarter)
customer(customer_id,name,address,member_card)
fact tables
Sales(item_id,store_id,date_id,customer_id,unit_sold,cost)
My question is if I want to find average sales of a location for a month Should I add average_sales column in fact table and if i want to find sales done using the membership card should I add corresponding field in fact table?
My understanding so far is only countable measures should be in fact table so I guess membership_card should not come in fact table.
Please let me know if I am wrong.

No, you should not add an average sales column to your fact table, it is a calculated value, and is not at the same "grain" as the fact table.
Your sales fact table should be as granular as possible, so it should really be sales_order_line_items, one row per sales order line item.
You want to calculate the average sales of a given store for a given month...?
First, by "sales" do you mean "revenue" (total dollars in) or "quantity sold"?
Average daily revenue?
Average monthly revenue, by month?
If you have the store id, date, quantity sold (per line item) and unit price, then it's pretty easy to figure out.

You Should not add aggregate columns In the same fact table. The measures in the fact table should be at the same grain. So if you want aggregate metrics, build a separate fact table at the required grain.
So, I might have a fact aggregate table named F_LOC_MON_AGG which has the measures aggregated at location and month level.
If you do not have aggregate tables, modern business intelligence tools such as OBIEE can do the aggregation at run time.
Vijay

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I have transactional data for a sales team showing the transaction amount per transaction, the sales person for that transaction, his team and his salary. Every row denotes a unique transaction (please refer image). I need to make a team-level graph which shows the correlation between the salary they are paid and the revenue they generate for the company i.e. a simple stacked bar chart with salesTeam name on X axis and amounts on the y axis with every bar representing the total salary and total revenue(Amount) for a team.
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Thanks
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However, if this is not possible the good news is the answer is a Level of Detail expression (i recommend doing some reading on this if you havent come across before). Basically, you tell Tableau at what level you want the calculation at.
If I understand you want to calculate the ratio of transaction amount and salary paid for each team.
So create a calculated field as follows:
{ FIXED [Team]
: sum(([Amount]))/
(sum({ FIXED [Sales person]:
AVG([Salary])}))
}
What this does is calculates for each team the ratio between the amount and the salary. The use of the second fixed equation that is nested within it (Salesperson) ensures that the salary is not summed for the number of transactions of a salesperson.
Using this I got a result of 17.2 for Central. Is this what you would expect? Do you need a way to account for salaries that are not known?

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here is what worked:
sum(
(
[Time].[Week].[All],
[Product].[Product Number].[All],
[Time].[Month].[All].[Y],
[Customers].[Customers].[All].[X]
),Measures.[Sales]
)
+ ... repeat ....
Thanks for the help!!

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