By default DynamoDB will make a new entry if an object with the specified index doesn't exist. Is there a way to stop this from occurring? I could just query the table for the key before updating, but it would be nice to do it all in one request.
推荐答案
使用条件表达式 id = :id 其中 id 是属性名(或主键名您的情况)和 :id 是值(您要更新的项目的键).
Use conditional expression id = :id where id is the attribute name (or primary key name in your case) and :id is the value (key of the item you want to update).
Conditional expression is always evaluated before any writing. If that expression doesn't evaluate to true (and it doesn't if that key doesn't exist or is different), it doesn't update or put a new item.
