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Have you ever thought about why the transaction and refund have to be split into different tables

2020-11-08 23:46:18 Liu Zhihang

Preface


Do new projects recently , When designing table structure , Suddenly I remembered a question I met in the interview before , At that time, I was just a beginner , A little knowledge of a lot of things ( Now, of course ), At that time, the little brother asked me why the transaction and refund had to be split into two tables ? Based on what considerations ? What are the benefits and advantages ?


official account :『 Liu Zhihang 』, Record the skills in work study 、 Development and source notes ; From time to time to share some of the life experience . You are welcome to guide !

background

It was a sunny afternoon , Of course , A sunny afternoon should be accompanied by other adjectives , It's just that I'm not very good at learning , This word can only be used as the beginning of the next …… ( The small five thousand words are omitted here )

Get into the text !

Because I've been doing it before Aggregate payment , And in the process of use , It's also a separate payment and refund form , Use it all the time , I don't think it's wrong .

For example, a trading table is basically like this :

Field type meaning
id bigint Primary key id
trans_id varchar Transaction order number
trans_amount bigint Order amount
trans_status tinyint Transaction status
…… …… ……
create_time datetime Creation time
update_time datetime Update time

The refund form is almost like this :

Field type meaning
id bigint Primary key id
refund_id varchar Refund order number
origin_trans_id varchar Original transaction order number
refund_status tinyint Refund status
refund_amount bigint Refund amount
…… …… ……
create_time datetime Creation time
update_time datetime Update time

Maybe that's how the two watches are ! For example, some other fields are omitted first , I don't think it's very important to use it .

But just that time the little brother asked this question , Why should payment and refund be recorded separately ?

At that time, strength did not allow , I just said that's how it works , Separate the forward flow from the reverse flow , Separate implementation logic , It's more convenient .

Personal opinion

It's not just about deals and refunds , At the same time, it generally refers to forward trading and reverse trading , Such as recharge and consumption , Borrowing and lending , Account out of the account into the account and so on , Here's just my personal opinion , Just a discussion , If the partner has a better idea , I hope you can leave a message indicating , Learning together .

Reconciliation requires

For accounts , The amount of the last two parties in the payment statement and the income statement can be correct , in other words Balance of payments .

Of course, it can be written in a table . After all, it's just a running account with no status change , For example, in the account , In the account , wait , The running chart can be recorded in one , Then use the field to identify whether it is an account or an account .

It takes

Reading materials on the Internet often says Sub database and sub table , And like orders ( transaction / refund ) Two kinds of business , It is relatively appropriate to use two tables , After all transaction There are a lot more orders than refund orders .

Field design

Transaction and refund are two completely different businesses , Unlike an account flow, it's a record of funds .

In addition to the order status, there are also some transaction information, such as merchant number 、 Preferential amount 、 Amount paid 、 Trading channels 、 goods id name 、 Notes and other information .

The refund is based on the original order , The original order number needs to be recorded 、 Refund amount ( Partial refund )、 Refund information, etc .

Although transactions and refunds generally include The order number 、 state 、 Amount, etc. , But if you force it into a table , It will lead to the following problems :

  1. Many fields are empty , For example, the transaction does not need the original order number , The original order number needs to be stored for refund . It is not appropriate to set the index to improve the query efficiency .
  2. States may not be fully compatible , Transaction status and refund status are difficult to be compatible with each other .

Development efficiency

After the transaction is separated from the refund , Two people are responsible for different business development , Including business logic and query presentation . If put together , Many fields can't guarantee that others will know whether there is or not , Is it to store or not to store , After all, all the settings in the table can be empty . It takes a lot of communication in this case , Or develop it on your own .

Design patterns and principles

Others from the perspective of design patterns and principles , It can be said that the responsibility is single , Of course, I can't pull it out even if I'm a big up leaning theory .

summary

Q&A

Q: The front end will show how to handle two or more in a list ?

A: In many APP The various orders you can see are displayed in a list , such as : Alipay's bill page .

Of course , If the front end is divided tab page , Show different businesses separately , That's hardly too friendly for the back end . But it's not always the case , At this time, we need to store the order in a unified way .

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Store in a public store when the order is successful , Can pass MQ etc. , Take the data to another table / library , perhaps ES Used to store . In this way, the order query can also be combined with the business logic table / Library separation . It can also be done through binlog To deal with , The plan here is for reference only .

Conclusion

The reason why I wrote this article , It is also to summarize the problems encountered in recent work , And how to deal with it . At the same time, I remember the same problem I met a long time ago .

If the partners have other opinions , Welcome to leave a message , Express your opinions and opinions , Discuss together .

版权声明
本文为[Liu Zhihang]所创,转载请带上原文链接,感谢

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