I have this scheme in CaseStudio where I have multiple instances of keeping the address of something. I have the adress of a client, address of an event, address of a user. And in order to have it in 3rd normal form I have a table called cities which has only "city" as PK and its ZIP code. But I do not know if I have to connect it to all the others tables which contain the name of the city, or if it can be without any relation to anything.
It is unlikely that this table would be unconnected to anything else. You would want the address to relate in some way to the city. Think how you would query the address, you would wan t return the person name (from your user or peopel table), the strett addess from you address table, the city from you city table. But you woudl have to know how each of these pieces of information are related to each other.
Personally I find that having a separate city and zipcode table is really overkill when it comes to addresses, but if this is an academic exercise, they might want you to break it out to get to the correct normal form. Normally in this case you would have a cityid as a column in the city table and then the address table would contain the cityid field and there would be a foriegn key set up to the city table to maintain teh data integrity.
Related
I'm making a sql database for a small company.. Pretty much the other tables don't relate to the question so ill list the two that do...
There is a table:
NextofKin:
fname
lname
street
no
houseno
city
AND
Patient:
ID[pk]
fname
lname
houseno
city
Pretty much would I need a seperate table for street, house and city?
also any idea what i could use as a primary key for NextOfKin?
Your questions are starting to get into database normalization.
What you should be doing is never duplicating data between tables unless that data relates the tables, and that data should be indexed. Something like this comes to mind ( there are different ways you might construct it based on business logic )
PersonalData: id, fname, lname, address1, address2, city, state, zip
Patient: id PK, personal_data_id FK, next_of_kin_id FK
Granted most of the tables already exist so this may be impossible. But to answer your question directly, since the database is not normalized already, there's no good place to put further address records ( don't want them under Patient right? ) and so you're stuck duplicating the data. Even so, there has to be some relationship between Patient and NextOfKin, so either Patient holds a reference to NextOfKin, or NextOfKin hods reference to Patient. Either way, you might consider using a foreign key between them to enforce, and explicitly state, this relationship.
Yes, use a pk for next of kin.
Use a joining table between patient and next of kin. Multiple patients could list the same person as next of kin, and while your app may not today require someone to designate multiple people as next of kin, they may change their mind in the future and your application will support it.
Myself, I always use a separate address table. Since usually more than one person lives in a house, and a person can have more than one home, you would again use a joining table.
I am creating the database structure of an ecommerce with Mysql and INNODB engine.
Point 1: To create multiple addresses for the customers i have this tables
Am I doing it in the correct way? And how should I store the default address (in which table)?
Point 2: I have another table called "Suppliers", should i just connect it to addresses with a "supplier_address" table or is there a better way?
Point 3: What about the tables cities and countries? Should i add something or is that ok? Maybe a field "district" in another table beetween the two?
In my view you're making this far too complex. There's no need to make your address schema so over-normalized. Most systems I've seen that handle multiple customer addresses have a customer table like yours, and then have an address table, as follows:
customer_id
address_ordinal (small number for each customer: 0,1,2,3 etc).
primary (boolean)
address_1
address_2
locality (city, village, etc)
province (state, etc)
postcode (zip, postcode etc)
country
customer_id is a foreign key to the customer table. The primary key is a composite of (customer_id, address_ordinal). The primary column is true if the address is the primary one.
Regarding your question about suppliers, you might want to create a common table called "contacts", and give both your customers and suppliers contact_ids.
If your system contains a reference table (perhaps something you purchase from a data supplier) containing (postcode, locality, province) rows, you can use that to help populate your address table. But you should avoid forcing your addresses to only contain hard-coded postcodes: those reference tables get out of date very fast.
I'll start out my answer with the ole cliche: "There's more than one way to skin a cat." That said, I have a few suggestions:
Point 1 - Assuming a customer can have multiple addresses (i.e. billing and mailing), then yes, you have the right idea in terms of the separate mapping table. As for adding a field to customer_addresses called default or preferred, or something like that, it's not a bad idea, but another option is to add a new field called address_type that would reference a separate table with two records, "Billing" and "Mailing" and/or whatever else you would want. Then, in whatever application you are coding that is going to use the address data, depending on what context i.e. if you're on the billing info page, then code the address type that you use on the page itself something like SELECT * FROM customer_addresses WHERE address_type = 2 /* Billing */.
Point 2 - Same as for customers.
Point 3 - Do you want to be able to display shortened country names? For example, abbreviate "United States" to "US," "Canada" to "CAN," or "United Kingdom" to "UK?" I'd consider adding a field for abbreviated country names for that purpose.
In my application each of my users is required to select a suburb to which to associate their profile. The users table has a field suburb_id and a table called suburbs has both an id and name field.
Our suburbs table contains most of the suburbs that we will need, however occasionally users will need to enter suburbs that we don't have in our table, or have popped up since we populated our table.
What is the best way in terms of database design to solve this problem.
I had considered changing the field suburb_id to just suburb and then testing in the application whether it was an integer or a string - if it was an integer the application would assume it is related to an item in the suburbs table, if it was a string it would assume otherwise. However, if a user was to simply enter an integer in the suburb field then the application would obviously mistake it and try to match it up with a value in the table.
Is that an acceptable way to deal with the problem (it seems gimmicky to me - I am sure there must be a better solution).
EDIT: I would also like to avoid inserting data provided from users into the suburbs table (even if flagged) as I don't want to affect the quality of the suburbs data we have.
There might be several ways to handle that, but I think the most clean way is to leave the suburbs and userstable as they are, and add the suburb to the suburbs table in case the suburb doesn't already exist. Maybe with a flag that this in an user generated entry for later cleanup.
I had considered changing the field suburb_id to just suburb and then testing in the application whether it was an integer or a string - if it was an integer the application would assume it is related to an item in the suburbs table, if it was a string it would assume otherwise.
That can lead easily to performance issues.
There's no magic bullet for this kind of problem. If there's a foreign key reference, you only have a few choices.
Let the user insert rows into the suburbs table.
Don't let the user insert rows into the suburbs table.
Remove the foreign key reference.
Replace the suburbs table with supertype/subtype tables, where the supertype would contain all suburbs, and the subtype tables would distinguish user-submitted suburbs from validated suburbs.
I have 3 entities:
buildings
activities
addresses
And I don't know how to foreign key the relationships between tables.
Buildings are located at addresses.
Activities are performed at addresses (one address at a time).
But I just want one address table.
Suppose the next attributes:
Buildings(id,phone,email,image,comments) <- should I put address_id ?
Activities(id,description) <- should I put address_id?
Addresses(id,street,city,state,postcode) <- or should I put center_id and activity_id here?
Thank you in advance!
You should use address_id both in buildings and activities tables.
Address is unique, while many buildings and many activities can be located to the same address!!
Your question implies that multiple buildings can be located at the same address - is this what you want? If so, just normalize it accordingly:
The Address is your 'root entity':
ADDRESS(address_id,street,city,state,postcode)
A Building can be located at exactly one Address, so include a reference to Address, a foreign key:
BUILDING(building_id,phone,email,image,comments,address_id)
An activity is performed at exactly one address, references to Address by foreign key:
ACTIVITY_ID(activity_id,description,address_id)
Maybe you should think about whether:
a street number is missing in the address?
should having more than one building at a given address be possible?
more than one address for a given building is possible (yes, I've seen this)?
a separate ADDRESS table is really necessary (see above questions)?
Alex, you should have the IDs in both tables, as you're saying in your question. There is no need to have them in separate tables as actually the address of a building will be where an activity will be performed, right?
If you are worried about two buildings having the same location then add a uniq index in the address_id column of the buildings table.
Moving a bit forward. Can you have an address without a building? If that is the case, then you could even add the address data (columns) to the buildings table. Because it would be a one-to-one relationship and no other entity would need to use the address table but the buildings one. That way you would get rid of the addresses table
I'm putting together a system to track customer orders. Each order will have three addresses; a Main contact address, a billing address and a shipping address. I do not want to have columns in my orders table for the three addresses, I'd like to reference them from a separate table and have some way to enumerate the entry so I can determine if the addressing is main, shipping or billing. Does it make sense to create a column in the address table for AddressType and enumerate that or create another table - AddressTypes - that defines the address enumeration and link to that table?
I have found other questions that touch on this topic and that is where I've taken my model. The problem I'm having is taking that into the cakePHP convention. I've been struggling to internalize the direction BelongsTo relationships are formed - the way the documentation states feels backwards to me.
Any help would be appreciated,
Thanks!
You are spot on. You could do either, depending on how much you want to normalise your database. Personally for me, I'd go with an AddressType model, which gives you the flexibility to add and remove address types at will.
If you want it simpler, then I would just go with an ENUM() field in your Address model.
I prefer to think of hasOne, hasMany and hasAndBelongsToMany as the three real relation types.
The belongsTo relation is there simply to do the reverse of what the former two (hasOne/Many) do.
If you look at this diagram, you will notice the pairing of hasOne/belongsTo and hasMany/belongsTo.
Also, note that model that "belongsTo" is the one storing the foreign key (eg. address_type_id).
So in your case, since an AddressType hasMany Address (ie. you can have many Home addresses), then the Address belongsTo AddressType (ie. each address needs an address_type_id).
Table1: address_types (id, name, active)
Table2: customers (id, name, active, etc.)
Table3: addresses (id, address_type_id, customer_id, country, city, street, etc.)
This way customers can have as many addresses as you want. If you need to add a new address type you must not alter the customers or addresses table.