列 「users.id」 必須出現在GROUP BY子句或在聚合函數可以使用

Question

關係：

Item belongs to Product 
Product belongs to User 

Item模型範圍：

scope :search, ->(search_term) { 
    select('products.name, users.*, products.brand, COUNT(products.id)') 
    .joins(:product => :user) 
    .where('users.name = ? OR products.brand = ?', search_term, search_term) 
    .group('products.id') 
    } 

在以下SQL上述結果聲明：

SELECT products.name, users.*, products.brand, COUNT(products.id) FROM "items" 
INNER JOIN "products" ON "products"."id" = "items"."product_id" 
INNER JOIN "users" ON "users"."id" = "products"."user_id" 
WHERE (users.name = 'Atsuete Lipstick' OR products.brand = 'Atsuete Lipstick') 
GROUP BY products.id 

這裏的問題是，出現錯誤：

ActiveRecord::StatementInvalid: PG::Error: ERROR: column "users.id" 
must appear in the GROUP BY clause or be used in an aggregate function 
LINE 1: SELECT products.name, users.*, products.brand, COUNT(product... 

有什麼可以解決這個問題？

Answer 1

從你可以看到，你應該嘗試包括users.id的GROUP BY子句中的錯誤：

.group('products.id, users.id')