問題：
Suppose I have a table of customers and a table of purchases.假設我有一張顧客表和一張購買表。 Each purchase belongs to one customer.每次購買都屬於一個客戶。 I want to get a list of all customers along with their last purchase in one SELECT statement.我想在一個SELECT語句中獲取所有客戶的列表以及他們的最後一次購買。 What is the best practice?最佳做法是什麼？ Any advice on building indexes?關於建立索引的任何建議？
Please use these table/column names in your answer:請在您的答案中使用這些表/列名稱：
- customer:
id,name客戶：id，name - purchase:
id,customer_id,item_id,date購買：id，customer_id，item_id，date
And in more complicated situations, would it be (performance-wise) beneficial to denormalize the database by putting the last purchase into the customer table?在更復雜的情況下，通過將最後一次購買放入客戶表來對數據庫進行非規範化是否（性能方面）有益？
If the (purchase) id is guaranteed to be sorted by date, can the statements be simplified by using something like LIMIT 1 ?如果 (purchase) id保證按日期排序，是否可以使用諸如LIMIT 1類的東西來簡化語句？
解決方案：
參考一： https://en.stackoom.com/question/8rGa參考二： https://stackoom.com/question/8rGa