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).
Related
Is it possible to order a to-many association using a foreign attribute?
For example: Say there are 3 entities Client , Order and Dish. For the sake of argument, say that there is a one-to-many association between Client and Order, and there is a many-to-one association between Order and Dish. And that Dish has a field named price
So, a client can put many orders, and each order corresponds to one dish.
I would want to sort the one-to-many association by the price of the dish. i.e. , to have a getOrders() method for the Client entity that returns the Orders sorted by $order->getDish()->getPrice().
I know that I could implement this function by using a Query (i don't want this, because i don't have access to the repository in the Client Entity), or by sorting the orders in memory (which is slower), but i would rather let Doctrine do the work.
Just use annotations
**
* #ORM\ManyToOne(targetEntity="Dish")
* #ORM\OrderBy({"price" = "DESC"})
*/
private $dish;
My answer is based upon your description but I'm not sure that one order could have only one dish (otherwise ordering would be useless, I'm I wrong?)
If you need to change relationship cardinality, of course, you can: the earth of the answer is OrderBy annotation
In AX2009, how is it possible to find the table that is related to an InventTransType in the code?
For instance, InvnetTransType::Sales is related to the SalesTable, but how is it possible to get the table id or table name from SalesTable in the code?
I do not think this is possible, because there is no 1:1 relationship between the elements of the InventTransType enum and tables. At best there is a 1:n relationship (e.g. you could argue that InventTransType::Sales is related to table SalesLine just as well or even better as table SalesTable). Note also that the documentation on the enum says that it specifies "the module that generated the transaction".
It really depends on the question you ask and the data you want to retrieve. That said, here are some points you could research, maybe one of them fits your question/requirements. If all else fails, you can always write your one mapping method that takes an enum element and gives you the id of the table you think is appropriate for this element(standard AX does this in several cases to map other entities to the enum elements, see for example table InventDimSetup, method transType2FieldId).
cross references: check the cross references of the enum or of an enum element, that should give you an idea which table(s) are associated with which element
relations of table InventTrans: for some of the enum elements, you can find table relations in table InventTrans (but unfortunately not for all of them); ponus point is that by using reflection, you can analyze the relations and get the referenced table (which is probably as close to your requirement as it can get in standard AX)
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.
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.
I am using EF 4.1 RC and CodeFirst/POCO to build my database by code.
Imagine having a many-to-many relationship like Teachers-Students (one teacher can have many students, and one student may have many teachers). Accordingly I have two POCOs: (1) Teacher and (2) Student.
When EF creates the corresponding tables you will end up with three tables: (1)Teachers, (2) Students and (3) an extra join table. The join table contains exactly two fields: a Teacher_ID and a Student_ID.
I was wondering if I had any chance to add an extra field to the join table, e.g. "Grade" (the grade a certain teacher gives a certain teacher)?
Currently I have no idea how to achieve this with only two POCOs.
So I guess all I can do is create a third POCO (for the join table) manually, am I right? That will certainly work, but then I am losing nice navigation properties like oneTeacher.Students.First(), etc. That is the main reason why I am still looking for another way.
That's correct, and does not only apply to Code-first. If you have extra fields in your joining table, you will have it mapped as an entity. And vice-versa, if you want an extra field in your joining table, you need to create a new entity and have zero-or-one-to many or one-to-many navigation properties to the Teacher and Student entities. In any case, you lose the comfort of accessing Teacher.Students and Student.Teachers and have to go via the intermediate entity.
Alternatively, you could think about modeling the DB structure differently and extracting the extra info into the Teacher or Student or a fourth entity. But that depends entirely on your scenario.
Yes, the join table cannot have a payload or you need to break it down to 2 one to many association which will result in creating a third entity to hold the PKs as well as the additional properties.
This is an idea I still haven't found time to try it out. Maybe you can keep your Student and Teacher classes as they are, and add a third POCO StudentGrade with properties Student, Teacher and Grade. Then you'll have to use the fluent API to make sure that both the many to many relation between Student and Teacher and the StudentGrade class map to the same table.
Hope that helps