问题的核心

当人问一个问题 - 需要store多久的data，什么时候删除其他的

- 除了回答表面的不删除

- 还要回答深层的cost 问题

当人问一个问题 - 需要怎么弄Data

- 除了回答怎么弄

- 还有回答怎么用我们的tool来弄

对于过去的做过project，需要脑子里随时能够拿出summary

Sell-in/Sell-out

https://brandalyzer.blog/2016/07/12/sell-in-sell-out-and-sell-through/#:~:text=Sell%2Din%20refers%20to%20sales%20from%20manufacturers%20to%20distributors.&text=Sell%2Dout%20is%20sales%20from,Bestbuy%20to%20purchase%20a%20product.