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I am tyring to write a query that will give me the customer counts on a rolling 52 week ending on monthly basis. I can't seem to find anything anywhere that will help me. I am trying to avoid pulling the query 12 times to get the 52 week customer counts ending for each month!
this is what I have so far:

Hi community,
first of all, sorry for my bad english, I'm doing by best!
I've a question. I need to get database-entries for the last full 20 weeks, but the query should be dynamic.