Database export sql - Please tell me how to write mysql batch database export statement. Can it be implemented in one sentence?

Mysql export sql

<code> 订单表trade字段：stock_num   已使用库存数字段：num         商品总数字段：num_iid         商品id</code>

<code> 商品表goods字段：total_stock_num   总库存数字段：num_iid         商品id</code>

Requirements to achieve:
Automatically reduce the number of total_stock_num, then set it to stock_num, and update the value of total_stock_num at the same time

Note:
1. stock_num may already have a value, where to reduce When adding the original value, it is required that stock_num2. total_stock_num may be 0, may be less than num (then subtract as much as you want), or may be greater than num (this can be subtracted directly)

I don’t have any coins, what should I do? Can anyone help me with the answer? Thank you
Since there are thousands of orders to be shipped out in batches, what I currently think of is to query and process them in the program, but this will require a lot of SQL to be executed

<code> 例子1:stock_num=2   num=5   total_stock_num=100出库后：stock_num=5   num=5   total_stock_num=97</code>

<code> 例子2:stock_num=0   num=5   total_stock_num=100出库后：stock_num=5   num=5   total_stock_num=95</code>

<code> 例子3:stock_num=2   num=5   total_stock_num=2出库后：stock_num=4   num=5   total_stock_num=0</code>

Reply content:

Use MYSQL -uroot -p123