Generating Running Sum of Ratings in SQL
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Published on 2010-05-25T04:26:29Z
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postgresql
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I have a rating table. It boils down to:
rating_value created
+2 april 3rd
-5 april 20th
So, every time someone gets rated, I track that rating event in the database.
I want to generate a rating history/time graph where the rating is the sum of all ratings up to that point in time on a graph.
I.E. A person's rating on April 5th might be select sum(rating_value) from ratings where created <= april 5th
The only problem with this approach is I have to run this day by day across the interval I'm interested in. Is there some trick to generating a running total using this sort of data?
Otherwise, I'm thinking the best approach is to create a denormalized "rating history" table alongside the individual ratings.
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