How do I select top N rows grouped by a specific column in big query?-CodePudding

I have a database of (changed items/data) grocery story aisles and products, and I'm trying to find the top 3 most expensive items in each aisle that are in stock.

My code for big query is this:

SELECT ROW_NUMBER() OVER (PARTITION BY aisle ORDER BY price DESC) AS high_prices, aisle, 
price, product FROM `a_database.shopping.grocery_stores`
WHERE in_stock = TRUE AND high_prices <= 3
GROUP BY aisle 
ORDER BY price;

I am receiving an error of: unrecognized name: high_prices at [2:30] due to the high_prices <= 3, however, I don't know another approach to this.

I am expecting an output of the 4 most expensive items by aisle in the store that are in stock, as said. but it doesn't work due to above error. When I remove high_prices <= 3, instead I'm getting a list of all items in the store along with their aisles completely out of order.

The expected output is similar to this screenshot:

I have included a sample data table:

aisle    product        in_stock    price
1        fresh_chicken  TRUE        10
2        frozen_fish    TRUE        10
3        truffles       TRUE        15
2        cereal         TRUE        5
2        cake           TRUE        25
3        wine           TRUE        30
1        fresh_fish     TRUE        15
1        fresh_beef     TRUE        10
2        seasonings     FALSE       15
3        whiskey        TRUE        25
1        whiskey        TRUE        40
1        pre_cooked     TRUE        30
2        fresh_pie      FALSE       10
3        fresh_salad    FALSE       5

Any help or advice with this is greatly appreciated.

CodePudding user response：

Use below

select *
from your_table
where in_stock
qualify 3 >= row_number() over(partition by aisle order by price desc)

if applied to sample data in your question - output is

CodePudding user response：

Use HAVING if you want to reference aliases

SELECT *  FROM
    (SELECT ROW_NUMBER() OVER (PARTITION BY aisle ORDER BY price DESC) AS high_prices, aisle, 
       price, product 
    FROM `a_database.shopping.grocery_stores`
    WHERE in_stock = TRUE
    GROUP BY aisle ) t1 
WHERE high_prices <= 3
ORDER BY price;

CodePudding user response：

Use subquery:

select *
from (select row_number() over (partition by aisle order by price desc) row_number,
             aisle,
             price,
             product
      from a_database.shopping.grocery_stores
      where in_stock is true) a
where row_number <= 3