如何在objectBox flutter中连接表

Question

In my flutter project im doing offline module using objectBox database .In this module i have three tables ItemMaster table, customerMaster table and customerWiseStock table. I have the data of itemMaster and customerMaster tables and i want to get stock it depends on itemId(ItemMaster) and salestypeId(CustomerMaster) .

How to do anyone help?

here i have attach the picture for refrence.

Answer 1

First, it's important to acknowledge that ObjectBox is not relational DB and that one cannot always apply relational mechanisms.

Here's how you would typically approach this using ObjectBox:

1. Define relations between your entities (you don't need to model ID properties)
2. Define your query for the main result type and use links to "join" the other types in the query
3. From the result objects, you traverse the relations from a "main type" object to get the other types and thus to any property.

Note: ObjectBox is extremely fast when it comes to creating objects. So traversing related objects is usually a no-issue, especially when done in a transaction .

Answer 2

Mixing up "columns" from separate "tables" is not something you can do with ObjectBox. It is statically typed (and withs static schema), meaning the Dart objects are mapped directly to the data stored in the database. What you're describing is something you'd expect from an SQL database, with dynamic results (Dart type could be something like List<Map<String, dynamic>> ).

If you want to use an object database (not limited to ObjectBox), I suggest you think about de-normalizing your data where it makes sense. With ObjectBox relations (links) you should be able to achieve the same, but with fewer classes and still in a type-safe manner.

If you have some concrete Dart code (classes for the "entities") and an the data you want to query, I may be able to provide suggestion on how to clean things up.