Using the latest docker image (8.6.2) and MySQL 5.7 with an existing database structure to test out Directus.
Trying to create a Many to One relationship between 2 collections and the option is simply not selectable.
Many to One
I have created a new collection and the option to add the Many to One relationship is possible but not on existing objects. This happens on all situations no matter what the 2 collections are in the relationship.
There are existing foreign keys between the tables and I have tested on FKs with and without cascades. In all situations the Many to One option is not selectable.
Any ideas ...?
Related
I have 5 different models....similar structure but seperated due to lots of record so easier management and scalability.
I'm not sure if this is possible with django, but i have a div on the website which is called latest....i want to grab the latest 3 records and show it in this div....however having 5 different models its difficult....each have a timestamp field. Is it possible to query something like show latest 3 records in total, but check 5 of these models and display?
Usually if it was in one model I could have just easily said show latest x....but separated models makes its complicated. So i don't want to grab latest 3 records from each model....rather 3 in total but just consider from 5 different models and show latest 3 (either through filtering of id of timestamp field)
Please kindly let me know if there is a solution.
There is two different solution.
At first you can merge models and make a general model with common columns and each of 5 models connect to general model with ForeignKey. So you can make query on general model and access specific columns with related objects.
Second way is usingdjango contenttypes framework
I have 4 tables in my database. The image below shows the rows and columns with the name of the table enclosed in a red box. 4 tables total. Am I going about the relationship design correctly? This is a test project and I am strongly assuming that I will use a JOIN to get the entire set of data on one table. I want to start this very correctly.
A beginner question but is it normal that the publisher table, for example, has 4 rows with Nintendo?
I am using Django 1.7 along with PostgreSQL 9.3. I aim to keep simple with room to grow.
Basically you've got the relations back-to-front here...
You have game_id (i.e. a ForeignKey relation) on each of publisher, developer and platform models... but that means each of those entities can only be related to a single game. I'm pretty sure that's not what you want.
You need it the other way around... instead put three foreign keys onto the game model, one each for publisher, developer and platform.
A ForeignKey is what's called a many-to-one relation. In this example I think what you want is for 'many' games to be related to 'one' publisher. Same for developer and platform.
is it normal that the publisher table, for example, has 4 rows with Nintendo?
No, that's is an example of why you have it backwards. You should only have a single row for each publisher.
yes you are correct in saying that something is wrong.
First of all those screen shots are hard to follow, for this simple example they could work but that is not the right tool, pick up pen and paper and sketch some relational diagrams and think about what are the entities involved in the schema and what are their relations, for example you know you have publishers, and they can publish games, so in this restricted example you have 2 entities, game and publisher, and a relation publish among them (in this case you can place a fk on game if you have a single publisher for a game, or create an intermediary relation for a many to many case). The same point can be made for platform and games, why are you placing an fk to game there, what will happen if the game with id 2 will be published for nintendo 64 ? You are making the exact same mistake in all the entities.
Pick up any book about database design basics, maybe it will help in reasoning about your context and future problems.
I am using django and have three objects: Customer, Location and Department. Each has a related Setting object.
Is it better form to create a single table with optional/null foreign keys?
Or to create a different setting object/table for each of the 3 entities?
There are a few options
Create a separate Settings table and have a nullable ForeignKey from all of your objects to the Settings table. If you choose this option, you should create an abstract base class that has a ForeignKey to the Settings table and inherit from that abstract base class. That way you don't have to add the ForeignKey every time you create a new model.
Create a separate Settings table and use GenericForeignKeys from the Settings table to reference your object (Customer, Location, and Department). This has the advantage of not having an extra column in all of your tables that need settings. However, you can't do DB joins with GenericForeignKeys via the Django ORM's normal API. You'd have to use raw sql. Also, select_related doesn't work on GenericForeignKeys so you'd have to use prefetch_related instead.
Store the settings in a column in the database. You should interact with the data in some format (I like JSON) and then serialize it to a string to store in the DB. Then to read the settings, you could deserialize the string back into JSON and interact with it. With this method, you wouldn't need to join with another table to get settings, and wouldn't need to run migrations every time you added new settings. You also wouldn't need a separate Settings table. However, constructing a query to find objects with certain settings would be a pain the query would probably be slow as well.
Each option has its pros and cons; so, pick your poison ;)
Can Django support Oracle nested tables or varrays or collections in some manner? Asking just for completeness as our project is reworking the data model, attempting to move away from EAV organization, but I don't like creating a bucket load of dependent supporting tables for each main entity.
e.g.
(not the proper Oracle syntax, but gets the idea across)
Events
eventid
report_id
result_tuple (result_type_id, result_value)
anomaly_tuple(anomaly_type_id, anomaly_value)
contributing_factors_tuple(cf_type_id, cf_value)
etc,
where the can be multiple rows of the tuples for one eventid
each of these tuples can, of course exist as separate tables, but this seems to be more concise. If it 's something Django can't do, or I can't modify the model classes to do easily, then perhaps just having django create the extra tables is the way to go.
--edit--
I note that django-hstore is doing something very similar to what I want to do, but using postgresql's hstore capability. Maybe I can branch off of that for an Oracle nested table implementation. I dunno...I'm pretty new to python and django, so my reach may exceed my grasp in this case.
Querying a nested table gives you a cursor to traverse the tuples, one member of which is yet another cursor, so you can get the rows from the nested table.
I've started a model with the default, automatically handled IDs Django provides.
Now I've started interfacing with an external system which has its own IDs for the same objects, and it would be very convenient to align my own IDs with the external system's.
However, the numerical ranges overlap, so a naive solution wouldn't work.
Is there some elegant way to alter the IDs in a safe manner? (the object have multiple foreign keys/m2ms etc)
Thanks
I don't know if this is the best way but I would set all foreign/m2m keys to cascade updates and add a defined number to all IDs in the django db to remove the overlapping of the ranges (10k or 100K or more depeding on your data).
with that done, you can copy IDs from the other system. For safety, I would duplicate the ID columns while doing that in order to not lose the original ones... until sure all works ok