I have a collection of data like so
Programme title | Episode | Subtitle | Performers | Description
Initially I normalised this into two table like so
PROGRAMME
progid | progtitle | description
EPISODE
epid | progid | episode | subtitle | description
I'm thinking I'd like to represent the performers in another table though, but not sure how to represent it. From what I can tell the following relationships exist
One to Many: A programme can have many performers
One to Many: A performer could feature in many programmes
I'm not sure how I would represent this?
EDIT Ah I see so I'd actually have tables like this for example?
PERFORMER
performerid | performer
PROGRAMME
progid | progtitle | description
EPISODE
epid | progid | episode | subtitle | description
PROG_PERFORMER
progid | performerid
Also, performers can change between episodes
It's many-to-many. One performer can be in multiple programs, and one program can have multiple performers.
There's plenty of information on the net (and in textbooks) about setting up many-to-may relationships. One such resource is here:
http://www.tekstenuitleg.net/en/articles/software/database-design-tutorial/many-to-many.html
Really, though it should be
A Program has a one-many relationship with episodes
An episode has a many-many relationship with performers.
This is enough to create a query that will list all performer/show/episode relationships.
beside performer table you have to create a relation table
performer table
performerid | name | ...
relation table
performerid | progid
Related
I'm looking for some guidance, what's the best way to transform data from A to B. I.e. if each client has different data but essentially recording the same details, what is the best way to transform this into a common schema?
Simple example showing different schemas
Client A | Id | Email | PricePaid | Date |
Client B | Id | Email | Price | DateOfTransaction |
Result schema
| Id | Email | Price | Order_Timestamp |
This simple example shows two clients record essentially the same things but with different names for the price and date of the order. Is there a good technique to automate this for any future schema but purely through configuration? I.e. maybe something with XML/ XSD perhaps?
Many suggestions welcome.
Thanks,
I'm trying to create a friendship site. The issue I'm having is when a user joins a website they have to fill out a form. This form has many fixed drop down items the user must fill out. Here is an example of one of the drop downs.
Drop Down (Favorite Pets)
Items in Favorite Pets
1. Dog
2. Cat
3. Bird
4. Hampster
What is the best way to store this info in a database. Right now the profile table has a column for each fixed drop down. Is this correct database design. See Example:
User ID | Age | Country | Favorite Pet | Favorite Season
--------------------------------------------------------------
1 | 29 | United States | Bird | Summer
Is this the correct database design? right now I have probably 30 + columns. Most of the columns are fixed because they are drop down and the user has to pick one of the options.
Whats the correct approach to this problem?
p.s. I also thought about creating a table for each drop down but this would really complex the queries and lead to lots of tables.
Another approach
Profile table
ID | username | age
-------------------
1 | jason | 27
profileDropDown table:
ID | userID | dropdownID
------------------------
1 | 1 | 2
2 | 1 | 7
Drop Down table:
ID | dropdown | option
---------------------
1 | pet | bird
2 | pet | cat
3 | pet | dog
4 | pet | Hampster
5 | season | Winter
6 | Season | Summer
7 | Season | Fall
8 | Season | spring
"Best way to approach" or "correct way" will open up a lot of discussion here, which risks this question being closed. I would recommend creating a drop down table that has a column called "TYPE" or "NAME". You would then put a unique identifier of the drop down in that column to identify that set. Then have another column called "VALUE" that holds the drop down value.
For example:
ID | TYPE | VALUE
1 | PET | BIRD
2 | PET | DOG
3 | PET | FISH
4 | SEASON | FALL
5 | SEASON | WINTER
6 | SEASON | SPRING
7 | SEASON | SUMMER
Then to get your PET drop down, you just select all from this table where type = 'PET'
Will the set of questions (dropdowns) to be asked every user ever be changed? Will you (or your successor) ever need to add or remove questions over time? If no, then a table for users with one column per question is fine, but if yes, it gets complex.
Database purists would require two tables for each question:
One table containing a list of all valid answers for that question
One table containing the many to many relation between user and answer to “this” question
If a new question is added, create new tables; if a question is removed, drop those tables (and, of course, adjust all your code. Ugh.) This would work, but it's hardly efficient.
If, as seems likely, all the questions and answer sets are similar, then a three-table model suggests itself:
A table with one row per question (QuestionId, QuestionText)
A table with one row for each answer for each Question (QuestionId, AnswerId, AnswerText)
A table with one row for each user-answered question (UserId, QuestionId, AnswerId)
Adding and removing questions is straightforward, as is identifying skipped or unanswered questions (such as, if you add a new question a month after going live).
As with most everything, there’s a whole lot of “it depends” behind this, most of which depends on what you want your system to do.
I'm trying to create a database for a frienship website I'm building. I want to store multiple attributes about the user such as gender, education, pets etc.
Solution #1 - User table:
id | age | birth day | City | Gender | Education | fav Pet | fav hobbie. . .
--------------------------------------------------------------------------
0 | 38 | 1985 | New York | Female | University | Dog | Ping Pong
The problem I'm having is the list of attributes goes on and on and right now my user table has 20 something columns.
I feel I could normalize this by creating another table for each attribute see below. However this would create many joins and I'm still left with a lot of columns in the user table.
Solution #2 - User table:
id | age | birth day | City | Gender | Education | fav Pet | fav hobbies
--------------------------------------------------------------------------
0 | 38 | 1985 | New York | 0 | 0 | 0 | 0
Pets table:
id | Pet Type
---------------
0 | Dog
Anyone have any ideas how to approach this problem it feels like both answers are wrong. What is the proper table design for this database?
There is more to this than meets the eye: First of all - if you have tons of attributes, many of which will likely be null for any specific row, and with a very dynamic selection of attributes (i.e. new attributes will appear quite frequently during the code's lifecycle), you might want to ask yourself, whether a RDBMS is the best way to materialize this ... essentially non-schema. Maybe a document store would be a better fit?
If you do want to stay in the RDBMS world, the canonical answer is to have either one or one-per-datatype property table plus a table of properties:
Users.id | .name | .birthdate | .Gender | .someotherfixedattribute
----------------------------------------------------------
1743 | Me. | 01/01/1970 | M | indeed
Propertytpes.id | .name
------------------------
234 | pet
235 | hobby
Poperties.uid | .pid | .content
-----------------------------
1743 | 234 | Husky dog
You have a comment and an answer that recommend (or at least suggest) and Entity-Attribute-Value (EAV) model.
There is nothing wrong with using EAV if your attributes need to be dynamic, and your system needs to allow adding new attributes post-deployment.
That said, if your columns and relationships are all known up front, and they don't need to be dynamic, you are much better off creating an explicit model. It will (generally) perform better and will be much easier to maintain.
Instead of a wide table with a field per attribute, or many attribute tables, you could make a skinny table with many rows, something like:
Attributes (id,user_id,attribute_type,attribute_value)
Ultimately the best solution depends greatly on how the data will be used. People can only have one DOB, but maybe you want to allow for multiple addresses (billing/mailing/etc.), so addresses might deserve a separate table.
I'm putting together a database that I need to normalize and I've run into an issue that I don't really know how to handle.
I've put together a simplified example of my problem to illustrate it:
Item ID___Mass___Procurement__Currency__________Amount
0__________2kg___inherited____null________________null
1_________13kg___bought_______US dollars_________47.20
2__________5kg___bought_______British Pounds______3.10
3_________11kg___inherited____null________________null
4__________9kg___bought_______US dollars__________1.32
(My apologies for the awkward table; new users aren't allowed to paste images)
In the table above I have a property (Amount) which is functionally dependent on the Item ID (I think), but which does not exist for every Item ID (since inherited items have no monetary cost). I'm relatively new to databases, but I can't find a similar issue to this addressed in any beginner tutorials or literature. Any help would be appreciated.
I would just create two new tables ItemProcurement and Currencies.
If I'm not wrong, as per the data presented, the amount is part of the procurement of the item itself (when the item has not been inherited), for that reason I would group the Amount and CurrencyID fields in the new entity ItemProcurement.
As you can see, an inherited item wouldn't have an entry in the ItemProcurement table.
Concerning the main Item table, if you expect just two different values for the kind of procurement, then I would use a char(1) column (varying from B => bougth, I => inherited).
I would looks like this:
The data would then look like this:
TABLE Items
+-------+-------+--------------------+
| ID | Mass | ProcurementMethod |
|-------+-------+--------------------+
| 0 | 2 | I |
+-------+-------+--------------------+
| 1 | 13 | B |
+-------+-------+--------------------+
| 2 | 5 | B |
+-------+-------+--------------------+
TABLE ItemProcurement
+--------+-------------+------------+
| ItemID | CurrencyID | Amount |
|--------+-------------+------------+
| 1 | 840 | 47.20 |
+--------+-------------+------------+
| 2 | 826 | 3.10 |
+--------+-------------+------------+
TABLE Currencies
+------------+---------+-----------------+
| CurrencyID | ISOCode | Description |
|------------+---------+-----------------+
| 840 | USD | US dollars |
+------------+---------+-----------------+
| 826 | GBP | British Pounds |
+------------+---------+-----------------+
Not only Amount, everything is dependent on ItemID, as this seems to be a candidate key.
The dependence you have is that Currency and Amount are NULL (I guess this means Unknown/Invalid) when the Procurement is 'inherited' (or 0 cost as pointed by #XIVsolutions and as you mention "inherited items have no monetary cost")
In other words, iems are divided into two types (of procurements) and items of one of the two types do not have all attributes.
This can be solved with a supertype/subtype split. You have a supertype table (Item) and two subtype tables (ItemBought and ItemInherited), where each one of them has a 1::0..1 relationship with the supertype table. The attributes common to all items will be in the supertype table and every other attribute in the respecting subtype table:
Item
----------------------------
ItemID Mass Procurement
0 2kg inherited
1 13kg bought
2 5kg bought
3 11kg inherited
4 9kg bought
ItemBought
---------------------------------
ItemID Currency Amount
1 US dollars 47.20
2 British Pounds 3.10
4 US dollars 1.32
ItemInherited
-------------
ItemID
0
3
If there is no attribute that only inherited items have, you even skip the ItemInherited table altogether.
For other questions relating to this pattern, look up the tag: Class-Table-Inheritance. While you're at it, look up Shared-Primary-Key as well. For a more concpetual treatment, google on "ER Specialization".
Here is my off-the-cuff suggestion:
UPDATE: Mass would be a Float/Decimal/Double depending upon your Db, Cost would be whatever the optimal type is for handling money (in SQL Server 2008, it is "Money" but these things vary).
ANOTHER UPDATE: The cost of an inherited item should be zero, not null (and in fact, there sometime IS an indirect cost, in the form of taxes, but I digress . . .). Therefore, your Item Table should require a value for cost, even if that cost is zero. It should not be null.
Let me know if you have questions . . .
Why do you need to normalise it?
I can see some data integrity challenges, but no obvious structural problems.
The implicit dependency between "procurement" and the presence or not of the value/currency is tricky, but has nothing to do with the keys and so is not a big deal, practically.
If we are to be purists (e.g. this is for homework purposes), then we are dealing with two types of item, inherited items and bought items. Since they are not the same type of thing, they should be modelled as two separate entities i.e. InheritedItem and BoughtItem, with only the columns they need.
In order to get a combined view of all items (e.g. to get a total weight), you would use a view, or a UNION sql query.
If we are looking to object model in the database, then we can factor out the common supertype (Item), and model the subtypes (InheritedItem, BoughtItem) with foreign-keys to the supertype table (ypercube explanation below is very good), but this is very complicated and less future-proof than only modelling the subtypes.
This last point is the subject of much argument, but practically, in my experience, modelling concrete supertypes in the database leads to more pain later than leaving them abstract. Okay, that's probably waaay beyond what you wanted :).
I have to generate a view that shows tracking across each month. The ultimate view will be something like this:
| Person | Task | Jan | Feb | Mar| Apr | May | June . . .
| Joe | Roof Work | 100% | 50% | 50% | 25% |
| Joe | Basement Work | 0% | 50% | 50% | 75% |
| Tom | Basement Work | 100% | 100% | 100% | 100% |
I already have the following tables:
Person
Task
I am now creating a new table to foreign key into the above 2 tables and i am trying to figure out the pros and cons of creating 1 or 2 tables.
Option 1:
Create a new table with the following Columns:
Id
PersonId
TaskId
Jan2012
Feb2012
Mar2012
Apr2013
or
Option 2:
have 2 seperate tables
One table for just
Id
PersonId
TaskId
and another table for just the following columns
Id
PersonTaskId (the id from table above)
MonthYearKey
MonthYearValue
So an example record would be
| 1 | 13 | Jan2011 | 100% |
where 13 would represent a specific unique Person and Task combination. This second way would avoid having to create new columns to continue over time (which seems right) but i also want to avoid overkill.
which would be a more scalable way to have this schema. Also, any other suggestions or more elegant ways of doing this would be great as well?
You can have a m2m table with data columns. I don't see a reason why you can't just put MonthYearKey, MonthYearValue on the same table with PersonId and TaskId
Id
TaskId
PersonId
MonthYearKey
MonthYearValue
It's possible too that you would want to move the MonthYearKey out into their own table, it really just comes down to common queries and what this data is used for.
I would note, you never want to design a schema where you are adding columns due to time. The first option would require maintenance all the time, and would become very difficult to query also.
Option 2 is definitely more scalable and is not overkill.
Option 1 would require you to add a new column every month and simple date based queries of your data would not be possible, e.g. Show me all people who worked at least 90% in any month last year.
The ultimate view would be generated from a particular query or view of your data.