Usually in self realtionship tutorials it is taught in a subordinative way. Eg.: employee X subordinated to employee Y.
I have this scenario bellow where the related players are actually the same person but with different accounts.
So I don't know whether this is right to use self relationship in this case.
(aka: also known as)
aka_id ----> id_player
One player account is not subordinated to another. Players can have multiple accounts but I'm willing to relate them so I can tell they belong to the same person. In the real scenario, there is no master account to relate them to. this is a NON-SUBURDINATIVE scenario.
I thought of not using relationship in this case and insert a random hash key tag to the aka column:
380 | player120 | ae65a3f01a
500 | player430 | ae65a3f01a
The question here is:
Is it right to use self relationships in non-subordinative scenarios?
From the way you describe the problem, you have two entities: players and aka (which I will call nicknames). These are two separate entities, and that usually suggests three tables:
Players
Nicknames
PlayerNicknames
The third table is a junction table that combines the first two. You might be able to put all the information you need about Nicknames in PlayerNicknames -- that is fine. However, if you have a requirement that all nick names be unique, then you definitely want a third table.
My guess is that you have a player name that is automatically a nick name. Great. When you create a player, also create an entry in the nicknames.
Related
I am creating a database for a community to store details of all their members along with those members' relations with each other.
For Instance: There is a family of 4. Mother, Father, Son and Daughter. The Son gets married to a girl from another family in the same community (Their data is also in the same database). The newly married couple has a new member soon. Also they need to add their grand parents to the database at a later stage (Parents of both the Mother and Father in this case).
What would be the best way to create a schema for such a database.
I have a schema called member_details that'll store all community members' data in a single table something like this.
member_details: ID | Name | Birthdate | Gender | Father | Mother | Spouse | Child
All members would have relations mapped to Father,Mother,Spouse,Child referenced in the same table.
Is this schema workable from a technical pov?
I just need to know if my solution is correct or is there a better way to do this. I know there are a lot of websites storing this kind of data and if someone could point me to the right direction.
I'd advice you to use two tables. One for members of community and one for relations beetween them. Something like this:
Members:
ID | Name | Birth | Gender
Relations:
First Member ID | Second Member ID | Relation
Where you use IDs from first table as foreign keys in second. That way you'll be able to add more relations types when you need it. By the way, I'd add a third table to store relation types, so it can work as a dictionary. Same thing for genders.
As usual, "it depends".
The first question is "how will you use this data?". What sort of questions do you expect the database to answer? If you want to show a person's profile with their relationships, that's pretty easy. If you want to find out how many children a person has, or who is the grandfather of a person, or the age of someone's youngest child, that could be a little harder.
The second question is "how sure are you these are the only relationships you want to store?" Perhaps you also want to store "neighbour", "team member", "engaged_to" - or maybe you need to store that information later on. Maybe you need to take account of people getting divorced, or remarrying.
The schema you suggest works fine for most scenarios, but adding a new type of relationship means you have to add a new column. There are no hard and fast rules, but in general it's better to add rows than columns when faced with events in the problem domain. Asking "who is this person's grandfather" requires a couple of self joins, and that's okay.
#ba3a suggests splitting the information about people from the information about relationships. This is much "cleaner" - and less likely to require new columns as you store more types of relationship. Showing a person's profile requires a query with lots of outer joins. Finding a grand parent requires self joins on the "relations" table.
I have a table Things and I want to add ownership relations to a table Users. I need to be able to quickly query the owners of a thing and the things a user owns. If I know that there will be at most 50 owners, and the pdf for the number of owners will probably look like this, should I rather
add 50 columns to the Things table, like CoOwner1Id, CoOwner2Id, …, CoOwner50Id, or
should I model this with a Ownerships table which has UserId and ThingId columns, or
would it better to create a table for each thing, for example Thing8321Owners with a row for each owner, or
perhaps a combination of these?
The second choice is the correct one; you should create an intermediate table between the table Things and the table Owners (that contains the details of each owner).
This table should have the thing_id and the owner_id as the primary key.
So finally, you well have 3 tables:
Things (the things details and data)
Owner (the owners details and data)
Ownerships (the assignment of each thing_id to an owner_id)
Because in a relational DB you should not have any redundant data.
You should definitely go with option 2 because what you are trying to model is a many to many relationship. (Many owners can relate to a thing. Many things can relate to an owner.) This is commonly accomplished using what I call a bridging table. (Which exactly what option 2 is.) It is a standard technique in a normalized database.
The other two options are going to give you nightmares trying to query or maintain.
With option 1 you'll need to join the User table to the Thing table on 50 columns to get all of your results. And what happens when you have a really popular thing that 51 people want to own?
Option 3 is even worse. The only way to easily query the data is to use dynamic sql or write a new query each time because you don't know which Thing*Owners table to join on until you know the ID value of the thing you're looking for. Or you're going to need to join the User table to every single Thing*Owners table. Adding a new thing means creating a whole new table. But at least a thing doesn't have a limit on the number of owners it could possibly have.
Now isn't this:
SELECT Users.Name, Things.Name
FROM Users
INNER JOIN Ownership ON Users.UserId=Ownership.UserId
INNER JOIN Things ON Things.ThingId=Ownership.ThingId
much easier than any of those other scenarios?
I have got an issue how to change a model of database:
For now we have predefined table Categories
and let's say tables Places and People which can be assigned to categories so it looks like this:
People <=> PeopleCategories <=> Categories <=> PlaceCategories <=> Places
(People can have many categories, categories can have many people, places can have many categories, categories can have many places)
But now there is a new requirement:
On person profile show all corresponding places based on categories (so far no problem) and add a tick box modeling some attribute (for example show on front-end as favorite place). The same from the other side on Place profile mark people assigned to at least one same category with a tick box.
I wonder whether there is some nice way to model this - the only thing which came to my mind is to add a new PeoplePlaces table but then I have to manually control whether people or places did not change their categories and they are still assigned and so on - There will be quite a problem with consistency of data which I will have to manage on application layer.
The second thing I could probably do is to delete categories totally and make it only on PeoplePlaces level but I will lose some simplicity for user: there are like 10 predefined categories which user can select so the linking between People and Places is quite automatic on front-end and only admin should see which places are assigned to which people and manage that tick box I was talking about
What would you suggest for this architecture? Thanks in advance! (It is a MySQL db if it is important for some kind of solution but this is more a general architecture thing)
If I understood your question correctly, you need to ensure that a person can only favor a place that is connected to the same category as the person herself?
If so, take a look at the following model:
We don't link the "endpoints" directly, and instead "link the links". This allows us to migrate PERSON_CATEGORY.CATEGORY_ID and PLACE_CATEGORY.CATEGORY_ID into the FAVORED_PLACE table, and "merge" them there, producing a single FAVORED_PLACE.CATEGORY_ID field (note FK1,FK2in the diagram above).
As a consequence, if a person is connected to a place, that must be done through a common category.
Furthermore, since CATEGORY_ID is outside PERSON_CATEGORY's PK, a particular combination of person and place can be used only once, even if they match through multiple categories. Effectively, you pick one common category as "special". If a place (or person) is removed from the special category, you'll need to pick another common category to serve as special. If there are no common categories left, the corresponding row in FAVORED_PLACE will not be allowed to exist anymore.
I don't think deleting Categories is a good idea.
What you are doing is introducing a new entity - PersonsFavouritePlaces - which relates People and Place directly rather than via a Category. It is sensible that a PersonsFavouritePlace be limited to a Person and a Place linked by Category, so it should probably reference PeopleCategories and PlaceCategories rather than the People and Category tables.
The table would look like:
create table PeopleFavourtiePlace
(
ID int not null, -- Primary key
PeopleCategoriesId int not null, -- FK to PK of PerpleCategories
PlaceCategoriesId int not null -- FK to PK of PlaceCategories
)
I don't know whether MySql supports cascading deletes, but if so the two FK's should have that turned on so when someone deselects a category (deleting the PeopleCategories row) if it linked to a favourite place in that category it too gets deleted.
However, if a person links to a place via multiple categories then it gets complicated....
This is my first question to stackoverflow so if i do something wrong please let me know i will fix it as soon as possible.
So i am trying to make a database for Tv Shows and i would like to know the best way and to make my current database more simple (normalization).
I would to be able to have the following structure or similar.
Fringe
Season 1
Episodes 1 - 10(whatever there are)
Season 2
Episodes 1 - 10(whatever there are)
... (so on)
Burn Notice
Season 1
Episodes 1 - 10(whatever there are)
Season 2
Episodes 1 - 10(whatever there are)
... (so on)
... (More Tv Shows)
Sorry if this seems unclear. (Please ask for clarification)
But the structure i have right now is 3 tables (tvshow_list, tvshow_episodes, tvshow_link)
//tvshow_list//
TvShow Name | Director | Company_Created | Language | TVDescription | tv_ID
//tvshow_episodes//
tv_ID | EpisodeNum | SeasonNum | EpTitle | EpDescription | Showdate | epid
//tvshow_link//
epid | ep_link
The Director and the company are linked by an id to another table with a list of companies and directors.
I am pretty sure that there is an more simplified way of doing this.
Thanks for the help in advance,
Krishanthan Lingeswaran
The basic concept of Normalization is the idea that you should only store one copy of any item of data that you have. It looks like you've got a good start already.
There are two basic ways to model what you're trying to do here, with episodes and shows. In the database world, we you might have heard the term "one to many" or "many to many". Both are useful, it just depends on your specific situation to know which is the correct one to use. In your case, the big question to ask yourself is whether a single episode can belong to only one show, or can an episode belong to multiple shows at once? I'll explain the two forms, and why you need to know the answer to that question.
The first form is simply a foreign key relationship. If you have two tables, 'episodes' and 'shows', in the episodes table, you would have a column named 'show_id' that contains the ID of one (and only one!) show. Can you see how you could never have an episode belong to more than one show this way? This is called a "one to many" relationship, i.e. a show can have many episodes.
The second form is to use an association table, and this is the form you used in your example. This form would allow you to associate an episode with multiple shows and is therefore called a "many to many" relationship.
There is some benefit to using the first form, but it's not really that big of a deal in most cases. Your queries will be a little bit shorter because you only have to join 2 tables to get episodes->shows but the other table is just one more join. It really comes down to figuring out if you need a "one to many" or "many to many" type relationship.
An example of a situation where you would need a many-to-many relationship would be if you were modeling a library and had to keep track of who checked out which book. You'd have a table of books, a table of users, and then a table of "books to users" that would have an id, a book_id, and a user_id and would be a many-to-many relationship.
Hope that helps!
I am pretty sure that there is an more simplified way of doing this.
Not as far as I know. Your schema is close to the simplest you can make for what I presume is the functionality you're asking for. "Improvements" on it really only make it more complicated, and should be added as you judge the need emerges on your side. The following examples come to mind (none of which really simplify your schema).
I would standardize your foreign key and primary key names. An example would be to have the columns shows.id, episodes.id, episodes.show_id, link.id, link.episode_id.
Putting SeasonNum as what I presume will be an int in the Episodes table, in my opinion, violates the normalization constraint. This is not a major violation, but if you really want to stick to it, I would create a separate Seasons table and associate it many-to-one to the Shows table, and then have the Episodes associate only with the Seasons. This gives you the opportunity to, for instance, attach information to each season. Also, it prevent repetition of information (while the type of the season ID foreign key column in the Episodes table would ostensibly still be an INT, a foreign key philosophically stores an association, what you want, versus dumb data, what you have).
You may consider putting language, director, and company in their own tables rather than your TV show list. This is the same concern as above and in your case a minor violation of normalization.
Language, director, and company all have interesting issues attached to them regarding the level of the association. Most TV shows have different directors for different episodes. Many are produced in multiple languages and by several different companies and sometimes networks. So at what level do you plan on storing this information? I'm not a software architect, so someone else can better answer this question than me, but I'd set up a polymorphic many-to-many association for languages, directors, and companies and an inheritance model that allows for these values to be specified on an episode-by-episode, season-by-season, or show-by-show basis, inheriting the value from its parent if none are provided.
Bottom line concerning all these suggestions: Pick what's appropriate for your project. If you don't need the functionality afforded by this level of associations, and you don't mind manually entering in repetitive data (you might end up implementing an auto-complete system to help you), you can gloss over some of the normalization constraints.
Normalization is merely a suggestion. Pick what's right for you and learn from your mistakes.
Im trying to use to define a one-to-many relationship in a single table. For example lets say I have a Groups table with these entries:
Group:
Group_1:
name: Atlantic Records
Group_2:
name: Capital Records
Group_3:
name: Gnarls Barkley
Group_4:
name: Death Cab For Cutie
Group_5:
name: Coldplay
Group_6:
name: Management Company
The group Coldplay could be a child of the group Capital Records and a child of the group Management Company and Gnarls Barkley could only be a child of Atlantic Records.
What is the best way to represent this relationship. I am using PHP and mySQL. Also I am using PHP-Doctrine as my ORM if that helps.
I was thinking that I would need to create a linking table called group_groups that would have 2 columns. owner_id and group_id. However i'm not sure if that is best way to do this.
Any insight would be appreciated. Let me know if I explained my problem good enough.
There are a number of possible issues with this approach, but with a minimal understanding of the requirements, here goes:
There appear to be really three 'entities' here: Artist/Band, Label/Recording Co. and Management Co.
Artists/Bands can have a Label/Recording CO
Artists/Bands can have a Management Co.
Label/Recording Co can have multiple Artists/Bands
Management Co can have multiple Artists/Bands
So there are one-to-many relationships between Recording Co and Artists and between Management Co and Artists.
Record each entity only once, in its own table, with a unique ID.
Put the key of the "one" in each instance of the "many" - in this case, Artist/Band would have both a Recording Co ID and a Management Co ID
Then your query will ultimately join Artist, Recording Co and Management Co.
With this structure, you don't need intersection tables, there is a clear separation of "entities" and the query is relatively simple.
A couple of options:
Easiest: If each group can only have one parent, then you just need a "ParentID" field in the main table.
If relationships can be more complex than that, then yes, you'd need some sort of linking table. Maybe even a "relationship type" column to define what kind of relationship between the two groups.
In this particular instance, you would be wise to follow Ken G's advice, since it does indeed appear that you are modeling three separate entities in one table.
In general, it is possible that this could come up -- If you had a "person" table and were modeling who everybody's friends were, for a contrived example.
In this case, you would indeed have a "linking" or associative or marriage table to manage those relationships.
I agree with Ken G and JohnMcG that you should separate Management and Labels. However they may be forgetting that a band can have multiple managers and/or multiple managers over a period of time. In that case you would need a many to many relationship.
management has many bands
band has many management
label has many bands
band has many labels
In that case your orginal idea of using a relationship table is correct. That is home many-to-many relationships are done. However, group_groups could be named better.
Ultimately it will depend on your requirements. For instance if you're storing CD titles then perhaps you would rather attach labels to a particular CD rather than a band.
This does appear to be a conflation of STI (single-table inheritance) and nested sets / tree structures. Nested set/trees are one parent to multiple children:
http://jgeewax.wordpress.com/2006/07/18/hierarchical-data-side-note/
http://www.dbmsmag.com/9603d06.html
http://www.sitepoint.com/article/hierarchical-data-database
I think best of all is to use NestedSet
http://www.doctrine-project.org/documentation/manual/1_0/en/hierarchical-data#nested-set
Just set actAs NestedSet
Yes, you would need a bridge that contained the fields you described. However, I would think your table should be split if it is following the same type of entities as you describe.
(I am assuming there is an id column which can be used for references).
You can add a column called parent_id (allow nulls) and store the id of the parent group in it. Then you can join using sql like: "Select a., b. from group parent join group child on parent.id = child.parent_id".
I do recommend using a separate table for this link because:
1. You cannot support multiple parents with a field. You have to use a separate table.
2. Import/Export/Delete is way more difficult with a field in the table because you may run into key conflicts. For example, if you try to import data, you need to make sure that you first import the parents and then children. With a separate table, you can import all groups and then all relationships without worrying about the actual order of the data.