I need to allow multiple Products to be present in a Cart. I do not want to increase a quantity column, I actually want the same Product entity in the Cart twice. I want to reuse the Product entities and not create a CartProduct intermediary too.
Cart ManyToMany Product
However, the table is created by doctrine:schema:update with a compound primary key of cart_id + product_id. This prevents me adding the same Product twice.
How do I solve this?
This is not the only use-case I have where I need a ManyToMany to support duplicate entries. Is this just not possible with Symfony2/Doctrine?
It's not so much a limitation of doctrine as it is of relational databases. Every row needs to have a unique primary key which, by default in Doctrine 2, would be product_id,cart_id.
The only way around it is to make yourself an explicit CartProduct entity and add at least one more column. Not that hard to do. Just establish OneToMany relations to it from Cart and Product.
Related
I have 2 entity product (sigle product: id, name, category and set: id, name). Set is compose with one or more product. I add relation ManyToMany between product and set. Symfony add entity set_product.
I want in product add « product preferential » (of set_product) in case the product is a set.
I don’t know if thinking is correct ? What is the good way ? Thank in advance.
First, if only set is composed by one or more product, you should use OneToMany (set can have one or more product).
I think your thinking with product preferential should work anyway.
I have several entities with relationships between them, and when I delete an entity related to another entity, the two entities are deleted. This is what I want. However, I would like to know which one is deleted last. So I have a listener "preremove" which is called twice. Once for the first entity, a second time for the second. But I do not know which one is deleted last. Do you have any ideas? thank you in advance
Check tables foreign keys. If your tables have OneToMany relation, record which stores foreign key, will be deleted first.
Can someone check my ERD, because I don't know whether I'm doing it correctly or not. I'm not sure about the difference between strong and weak entity, what I'm sure is that strong entity has their own primary key.
Other than that, is it correct i need to take Payment_ID as foreign key in my order table ? and what other attribute that i could have in my ORDER TABLE
Maybe some suggestion on what to add or improve on my ERD. Here i have a image for my ERD. Thank You
Entity Relationship Diagram
PAYMENT has an ORDER_ID and ORDER has a PAYMENT_ID. Having both fields is redundant, I would remove ORDER.PAYMENT_ID which would be a nullable field if customers don't pay immediately.
ORDER_DETAILS requires a PK, either a surrogate key ORDER_DETAIL_ID or the combination of ORDER_ID, ITEM_ID.
Can a PAYMENT use only one or more than one COUPON? The cardinality on the crow's foot line says more than one, but the PAYMENT.COUPON_ID field would allow only one. A nullable PAYMENT_ID in the COUPON table would be a better choice.
You have some doubtful minimum cardinalities. A CUSTOMER must place at least one ORDER? Ok, I can accept that. An EMPLOYEE must take at least one ORDER? So everyone in the company must take orders, and you're not going to record employees until they've taken an order? Also, every ITEM must be referenced in ORDER_DETAILS? Are you not going to want to record items on offer before they're ordered?
Finally, a note on terminology: your diagram is better called a table diagram, not an ERD. To be called an entity-relationship diagram, a diagram has to distinguish the concepts of the entity-relationship model. The style of diagram you used doesn't distinguish entity sets (i.e. ID fields) from value sets (non-ID fields) or entity relations (tables with single-field PK) from relationship relations (tables with composite PK, i.e. ORDER_DETAILS is a relationship relation).
I have several entities, that can have multiple relationships.
For example, i have following entitites:
entity_type
tag
tag_assignment
news_post
account
In entity_type table are described all entities that i have in my project (e.g. news posts, blog posts, messages, accounts, everything)
Entity_type table has just id and name fields, name field describes model class name for usability
Tag entity has just id and name. It's standalone entity, that is mapped to other entities later with tag_assignment entity
Tag assignment entity has id, tag_id, entity_type_id and entity_id. Entity_type_id describes in which i can find entity, entity_id specifies entity in the table.
So i want to make following combined foreig key from one column to many tables:
tag_assignment.entity_type_id => entity_type (id)
tag_assignment.entity_id => news_post (id), account (id), etc
Is it possible to make this combined key? I mean if to make dependencies if i delete a row from entity_type table, everything will be dropped/updated in other tables, if i will delete account, only tag_assignments that have foreign key to account table will be deleted.
You should normalize your database by extracting a table called entity. The concept of this table is similar to an abstract class in OOP. The news_post, account and other entities you might have in your database should all reference the entity table. This way you can reference any entity that you have now or might have in the future with a common, specific location.
Also you might want to familiarize yourself with the EAV model. This might help you resolve similar design issues.
Using Docrine2 entities, I have a "list" entity, with a manytomany relationship with "item".
I need to manipulate and save the order of the items in the list. I can't figure out how to accomplish this using Doctrine2. What I want is a joiner table that looks something like:
list_item
=========
list_id
item_id
sort_order
All I can find is this outdated to-do item: http://www.doctrine-project.org/jira/browse/DDC-213
Can I accomplish this using Doctrine? Or is there some other way I should be going about this?
Thanks.
Here is an exerpt from this docs section, that answers your question:
Real many-to-many associations are less common. [...] Why are many-to-many associations less common? Because frequently you want to associate additional attributes with an association, in which case you introduce an association class. Consequently, the direct many-to-many association disappears and is replaced by one-to-many/many-to-one associations between the 3 participating classes.