I would like to design a database using UML class diagrams but I dont know how. Can someone help me. How can I design a database using UML class diagrams?
Making an SQL database model in the form of a UML class diagram from a general information design model essentially requires to
Represent all entity types (or better: classes representing object types) as classes stereotyped as «object table» using SQL datatype names and replacing the UML {id} property modifier with a «pkey» stereotype:
Eliminate enumeration attributes for DBMS that do not support enumerations by connecting the object table with a corresponding enum table via a foreign key dependency arrow (a UML dependency stereotyped «fkey»):
Otherwise, as in the case of MySQL, you can use their syntax in the model like so:
Eliminate multi-valued attributes:
Eliminate associations:
Replace any functional association with a foreign key dependency:
Replace any many-to-many association (relationship type) with a class stereotyped as «association table» and two foreign key dependencies:
Eliminate generalization/inheritance relationships:
See this book chapter for more information.
you may try to start with a UML class diagram. Maybe you can find this tutorial useful - http://argouml-db.tigris.org/documentation/DB_UML_Guide.htm
You can additionally use "Relation scheme diagram" to design table relationship and clearly represent primary key / foreign key dependencies.
see this tutorial.
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I usually find everything I need, but there is first time for everything.. :D
I am trying to create a conceptual data model and I dont know how to properly show M:N relationship, which by default should not be included, but still you can assign verbs and directions of abstract entities. So let's say we have "Projects" and we have "Project roles", how do I properly show relationships? Can I have 2 arrows as showed in the picture or do I have to add join table and ?? I can't wrap my head around this..
Thank you so much in advance :)
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A conceptual data (or information) model can be created with a suitable modeling language, such as ER diagrams or UML class diagrams. Both languages have a concept and a visual notation for many-to-many associations (or relationship types). Simply follow their definitions. Since there is no standard for ER diagrams, it's easier/preferable to go with UML.
For showing a many-to-many association between two classes (representing entity types), you draw a connection line and annotate it with an asterisk ("*") at both ends.
Notice that a join table is a database implementation, and not a modeling concept.
I am trying to create a relational schema using this image.
But i don't know where to start. Can someone suggest some references to help get me started?
Start by specifying the types of facts that you want to record, in the form of predicate sentences with placeholders for values. For example:
The country with code <COUNTRY_CODE> is named <COUNTRY_NAME>
The language with code <LANGUAGE_CODE> is an official language of <COUNTRY_CODE>
<COUNTRY_CODE> has a <SUBDIVISION_TYPE> called <SUBDIVISION_NAME>
<COUNTRY_CODE> has a city called <CITY_NAME> in <SUBDIVISION_NAME>
Next, identify the domains of each placeholder as well as subset relationships between domains (these are your IS-A relationships and will eventually be enforced via foreign key constraints). Identify functional and multivalued dependencies, and normalize where required. If you kept your fact types simple you won't need much of the latter.
For more information, look into fact-based (i.e. relational) modeling disciplines like Object-Role Modeling.
I am trying to map the weak entity CatalogueEntry into a relational schema, and I am unsure which of the entities are the owner of this weak entity type. So, I don't know what the primary key of the relation in the relational schema is.
Anyone have any ideas? I have added an image below, thanks.
What is a Catalogue? Why doesn't catalogue appear on the diagram?
Sorry to ask stupid questions, but you learn to do that when you do data analysis.
It's useful to understand the data pretty well at the conceptal (ER) level, before switching to the relational level.
From the figure it shows that the weak entity CatelogueEntry depends on the Album strong entity by an identifying relationship (HasEntry).
For each catelogueEntry there must be an albumid. So here there are two tables. One is for Album and another table is for catelogueEntry. The catelogueEntry must contain a foreign key from album entry.
I have been having previous issues regards to class inheritance and structuring a database around this and using the entity framework to no success. So I have tried to create the entities inside visual studio and see what database tables it creates automatically.
I have a Entity MediaItem which is Abstract and Game Inherits from this. Game has a Console (Int) which corresponds to ConsoleID. However, when I generate the database I get an extra unwanted column (ConsoleTypes_ConsoleID) inside MediaItems_Game table. Why is this and how can I prevent this from happening? Thanks.
First of all your model is probably wrong. ConsoleType and Game is not in one-to-one relation (unless you have single game for each console type). I expect 1 console can have multiple games. So it should be one-to-many. In reality game can be released on multiple platforms so it should be many-to-many.
You got unvanted column because your relation between ConsoleType and Game doesn't know that it should use Console property as a foreign key. This happens if you use independent association. Independent associations are used by default when you draw them from one entity to other entity in Entity designer. You must use foreign key association.
Start with this set up (draw association from ConsoleType to Game - you must have one-to-many relation):
Select relation between ConsoleType and Game an in properties click on Referential Constraint:
In Referential Constraint dialog just set up relation:
Save your model and generate database again.
I created a class diagram for a system and now I have to model it into a real system. This means converting it to a database.
Now there is a base class which has just a few attributes, but there are many classes that inherit from it. Now my checklist for converting says I have to create a table for every class.
I don't know how to handle the inheritance, I can see that associations are done with PK and FK's but what about subclasses?
Is there some article which handles that or is there someone who can explain it to me?
Thanks in advance,
You have three alternatives to translate class hierarchies into relational tables:
- Create only a table for the superclass (all attributes and associations of subclasses are moved to the table corresponding to the superclass with the possibility of taking a NULL value)
- Create only tables for the subclasses: All attributes and associations of the superclass are repeated in each subclass
- Create tables both for the superclass and for each of the subclasses. In this case, the PK of the subclasses is at the same table a FK to the superclass (this ensures that all identifiers in a subclass table correspond to an existing identifier in the superclass table. A join between both tables allows to recover the full information of the element)
The best strategy depends on the problem (for instance, the number of attributes in each class, the number of levels in hierarchy, whether the hierarchy is disjoint or not,...)
If you want to see some examples, you can upload your hierarchy to the UMLtoDB online service http://modeling-languages.com/content/uml2db-full-code-generation-sql-scripts-databases
Drop all that UML nonsense - keep it simple. Its just amounts to duplication for no gain. Does Microsoft or Sun publish UML for dOT NET or Java... FOrgetting the odd sample, the majority of these frameworks dont have any official UML anywhere.
Usually, you design your datamodel (database tables/PK/FK etc.,) in parallel when you design your actual class diagram. After identifying all the cadidate classes and the dependencies on each of the classes, you will probably go on with the design sequence diagram. By this time, your data model should have been finalized.
I cannot understand your situation here, but IMO the process that you follow seems a bad idea to me.