理解一個軌的活動記錄查詢

Question

需要幫助，我有兩個型號

客戶和交易

Customer 
    has_many :transactions 

Transaction 
    belongs_to :customer 

現在我需要讓所有的客戶比1個交易

• 更在過去30天
• 剛剛在過去30天內的1筆交易

Answer 1

擴展在ScottJShea的答案，我會使用一些範圍

scope :one_recent_transaction, :conditions => lambda { 
    includes(:transactions).where("transactions.date > ?", DateTime.now - 30.days).group("customer.id").having("COUNT(transactions.id) = 1") 
} 

scope :many_recent_transactions, :conditions => lambda { 
    includes(:transactions).where("transactions.date > ?", DateTime.now - 30.days).group("customer.id").having("COUNT(transactions.id) > 1") 
} 

然後用它們這樣

one_transaction = Customer.one_recent_transaction 
many_transactions = Customer.many_recent_transactions 

Answer 2

您想使用HAVING子句。我建議（我猜測有點不完全知道你的模型）：

@exactly_one = Customer.where("transaction_date between ? and >", Date.now, Date.now - 30).group("customer.id").having("count(transaction.id) = 1") 

@exactly_one = Customer.where("transaction_date between ? and >", Date.now, Date.now - 30).group("customer.id").having("count(transaction.id) > 1")