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I want to use a rate system in my app , well I know how to implement RatingBar but I need to know the way I can calculate rating after each rate For example user 1 give 5 starts but 2 other users gives 3 , 4 starts, so what is the result in this case and how to calculate it ? there is a formula of calculation for this issue ?

Amine Choukri
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2 Answers2

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yes, you have to show the average rating

the formula is (sum of all ratings)/(count of total rating)

example 4 user give rating 1,2,3,5 respectively. then your formula be like
(1+2+3+5)/4
answer will be 2.75

Yogesh Choudhary Paliyal
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  • but in my table user there is 1 column of rating so i think i should calculate rating after each rate ? – Amine Choukri Jan 10 '18 at 13:16
  • no you have to put a query and code to calculate the average rating. – Yogesh Choudhary Paliyal Jan 10 '18 at 13:17
  • but how ?? for example the first user gived 5 stars i will store in the column 'rating' the value of 5 stars , the second user gived 2 stars and here i should update the column rating to get the new rating .. well for this example there is 2 users but in the real time i can't konw how much users even if i create a new table with id user1,id_user2,rate that's it ?? – Amine Choukri Jan 10 '18 at 13:22
  • you have to keep all the ratings with user id. create 2 colums only user_id & user_rating. – Yogesh Choudhary Paliyal Jan 10 '18 at 13:24
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If you have separate SQL tables for User and Ratings as tblUser and tblRatings respectively.

SELECT username, AVG(stars) AS average_rating
FROM tblUser
INNER JOIN tblRatings USING(mUserId)
GROUP BY mUserId
ORDER BY average_rating DESC, title;

Give your feedback if it helped of not. Happy to help more.

Er. Kaushik Kajavadara
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