Database schema for user reviews

Question

I am working on user reviews with this columns:

• product_id
• communication
• cleanliness
• location
• value

Each column can be number from 1-5. My question is how to calculate average grade for each column with out calling all reviews from database and calculating it every time.

So I was thinking to put in product table:

• communication_sum_of_grades
• communication_number_of_reviews
• ... etc

and than do: average= communication_sum_of_grades / communication_number_of_reviews

My question is if this is right approach?

Answer 1

If there are large number of records and query for average reviews are very frequent then your method will be efficient because in this case writing will be a touch heavy but reading will be very fast . But in case the query for average reviews is not that frequent then you may go for the triditional method of fetching all rows and finding avarage.

hope it helps :)