How to implement one-to-many relationships with DynamoDB

everyone! I have two tables that I would like to join via DynamoDb, but since the latter is not a relational db, I don't know how to map the link between the two tables.
In particular, I have a Price List table and a Detail List table that contains the details of the first one. How can I implement one-to-many relationship in java using dynamoDB with Spring Boot?

DynamoDB is basically a key-value store. You only every perform a lookup based on a key. That key may be artificial, not just a user id, but maybe "user_id#product#order" but still it will be a key-based lookup. If you want to use DynamoDB you have to store the data in a way that all queries that you will need will all boil down to basic key-based access (plus some sorting).
You have to do the exact opposite of normalizing your data and splitting relations into multiple tables: you have to de-normalize all your data to store the data and all the relations just in one table, multiple times, with multiple complex artificial keys. See e.g. https://www.youtube.com/watch?v=HaEPXoXVf2k on how to use LSIs, GSIs, how to model your data, how to choose artificial keys, etc.

That means you will not have Item, Order and OrderItem table that you join together, but you will have just one Everything table which may have the fields: userid, username, ordernumber, itemid, itemprice, itemquantity, itemname, orderdate, shippingaddress, etc.
And if you have three items in an order you will have three entries in this table. That means the username will be in the table very often, that means the itemname will be in the table very often and changing them will be difficult but that is how things are if you want to use dynamodb.

That is how you model one-to-many relations, by packing them into a single table and add proper indexes.

If you do have no idea about the current or future access patterns of your data or how to structure your data properly then dynamodb is the wrong tool for you.

The question you are asking gets at the very essence of working with DynamoDB and NoSQL data modeling. It is not as simple as applying your relational database knowledge to DynamoDB. Take a moment to familiarize yourself with the DynamoDB basics before you get too far into solving this problem.

Watch this video about modeling one-to-many relationships in DynamoDB. I would recommend you watch the entire video from the beginning, as it's one of the best introductions to the topic currently available.