[英]Active Record querying with joins and group by
I'm designing an API to get data from the following scenario :我正在设计一个 API 来从以下场景中获取数据:
brands
table : brands
表:
+------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | YES | | NULL | |
+------------+--------------+------+-----+---------+----------------+
items
table : items
表:
+---------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| category_id | bigint(20) | YES | MUL | NULL | |
| brand_id | bigint(20) | YES | | NULL | |
+---------------------------+--------------+------+-----+---------+----------------+
item_skus
table : item_skus
表:
+---------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| item_id | bigint(20) | YES | MUL | NULL | |
| number_of_stock | int(11) | YES | | NULL | |
+---------------------------+--------------+------+-----+---------+----------------+
Item
model association with ItemSku
and Brand
ItemSku
和Brand
Item
模型关联
belongs_to :brand
has_many :skus, class_name: 'ItemSku'
Simply i want the counts of stock available items and all items for each brand.只是我想要每个品牌的库存可用商品和所有商品的数量。
{
"brandCounts":[
{
"id":7006,
"name":"Brand 01",
"stockAvailableItemCount":50,
"allItemCount":60
},
{
"id":20197,
"name":"Brand 02"
"availableItemCount":150,
"allItemCount":660
}
]
}
Implementation :执行 :
brand_counts = []
brand_counts_hash = Hash.new()
items = Item.left_outer_joins(:skus).where(category_id: params[:id]).pluck(:brand_id, :number_of_stock, :item_id)
items.each do |item|
brand_id = item[0]
stock = item[1]
if brand_counts_hash.has_key?(brand_id)
item_count_arry = brand_counts_hash[brand_id]
stock_available_item_count = item_count_arry[0]
all_item_count = item_count_arry[1]
if stock > 0
brand_counts_hash[brand_id] = [stock_available_item_count + 1, all_item_count + 1]
else
brand_counts_hash[brand_id] = [stock_available_item_count, all_item_count + 1]
end
else
stock_available_item_count = 0
all_item_count = 0
if stock > 0
stock_available_item_count += 1
all_item_count += 1
brand_counts_hash[brand_id] = [stock_available_item_count, all_item_count]
else
all_item_count += 1
brand_counts_hash[brand_id] = [stock_available_item_count, all_item_count]
end
end
end
brand_counts_hash.each do |key, value|
stock_available_item_count = value[0]
all_item_count = value[1]
brand_counts << {
id: key,
name: get_brand_name(key),
stock_available_item_count: stock_available_item_count,
all_item_count: all_item_count
}
end
@brand_counts = brand_counts
render 'brands/counts/index', formats: :json
end
def get_brand_name(brand_id)
brand = Brand.find_by(id: brand_id)
brand.name unless brand == nil
end
Is there a way to optimize this further without multiple loops maybe?有没有办法在没有多个循环的情况下进一步优化?
Assume your Brand
model also has the following association defined假设您的
Brand
模型还定义了以下关联
has_many :items
and the final result you want is like你想要的最终结果就像
{
"brandCounts":[
{
"id":7006,
"name":"Brand 01",
"stockAvailableItemCount":50,
"allItemCount":60
},
{
"id":20197,
"name":"Brand 02"
"availableItemCount":150,
"allItemCount":660
}
]
}
The following code may not work when you copy and paste to your project.当您复制并粘贴到您的项目时,以下代码可能不起作用。 But it demonstrate how this problem can be solved with less code
但它展示了如何用更少的代码解决这个问题
Brand.includes(items: :skus).all.map do |brand|
{
id: brand.id,
name: brand.name,
stockAvailableItemCount: brand.items.count,
allItemCount: brand.items.map {|item| item.skus.sum(:number_of_stock)}.sum
}
end
if you need json format, just use to_json
to the result of above code.如果您需要json格式,只需将
to_json
用于上述代码的结果。
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