Unnest and Average operation in Couchbase - couchbase

Question

I have following structure saved in a bucket:
[
{
"Grouplens_1M": {
"genres": [
"Thriller",
"Drama"
],
"movieId": 3952,
"ratings": [
{
"rating": 4,
"userId": 23
},
{
"rating": 5,
"userId": 36
},
{
"rating": 4,
"userId": 52
}
],
"title": "Contender, The (2000)"
}
}
]
Now I need to get all titles which are rated in average above 3. I found out, that I need to unnest ratings and then use AVG to get the average. But it was not working. After trying to figure out how to solve this problem, I came to this:
SELECT g.title, AVG(r_item.rating) AS avg_r
FROM Grouplens_1M AS g
UNNEST ratings r_item
WHERE r_item > 4.0
GROUP BY g.title
After execution time on the query, it shows me a result. But the WHERE clause is not correct. It seems to ignore the statement as it shows me all movies with the average rating.

Answer 1

Since you want to filter out results based on the value of the derived average use HAVING. WHERE would be used to limit the documents considered for the query.
Try
SELECT g.title, avg_r
FROM Grouplens_1M AS g
UNNEST ratings r_item
GROUP BY g.title
LETTING avg_r = AVG(r_item.rating)
HAVING avg_r > 4.0;