问题：
Suppose I have a table of customers and a table of purchases.假设我有一张顾客表和一张购买表。 Each purchase belongs to one customer.每次购买都属于一个客户。 I want to get a list of all customers along with their last purchase in one SELECT statement.我想在一个SELECT语句中获取所有客户的列表以及他们的最后一次购买。 What is the best practice?最佳做法是什么？ Any advice on building indexes?关于建立索引的任何建议？
Please use these table/column names in your answer:请在您的答案中使用这些表/列名称：
- customer:
id,name客户：id，name - purchase:
id,customer_id,item_id,date购买：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?在更复杂的情况下，通过将最后一次购买放入客户表来对数据库进行非规范化是否（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保证按日期排序，是否可以使用诸如LIMIT 1类的东西来简化语句？
解决方案：
参考一： https://en.stackoom.com/question/8rGa参考二： https://stackoom.com/question/8rGa