database key value 数据库关键码值
The default values in the field would most likely be retrieved from a database or operational system, using the UPC symbol as the key value.
字段中的默认值很可能是通过使用upc符号作为键值从一个数据库或运营系统中检索到的。
Then when a value is set, the key is removed from the database and a new record is added with the updated value.
在设置一个值后,键就从数据库中移除掉,并添加一条具有更新过的值的新记录。
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