I'm looking for a good way say, to save favorite images for a specific user in the database. Or if I have a movie, I want to display related movies, you get the idea. I don't know how to do it on a database level (phpmyadmin). My idea so far is if I have a table named Users, I add a column in it named Favorites, in which I enter every ID or Name of the favorite item. The problem is that the content in this column may grow a lot more than I expect, and I don't feel this is a good way to do it. So how do I go about this?
Try having a table called "Favourites" with a column called UserID and another column for the ID or name of the favourited items. Then you would have one row for each user/favourite pair.
This allows you to have many favourites per user, and you can maintain arbitrary metadata about each favourited item (for example the time and which it was selected as the favourite).
You can also answer questions like "Which users have favourited a given item?" with this approach.
This is standard DB modelling for this type of problem.
Related
I'm having conception difficulties to implement something in a database. I have two solutions for a problem, and I was wondering which one is the best.
Problem :
Let's picture a table speciality with 2 fields : speciality_id and speciality_name.
So for example :
1 - Mage
2 - Warrior
3 - Priest
Now, I have a table user with fields such as user_id, name, firstname etc ...
In this table, there is a field called speciality. The speciality stores an integer, corresponding to the speciality_id of the table speciality.
That would be acceptable for users that have only one speciality. I want to improve the model to be able to have multiple specialities for a user.
Here are my two solutions :
Create a table 'solution1' which link the user_id with the speciality_id and remove the speciality field in the user table. So for a user which has 2 specialities, 2 rows will be created in the table 'solution1'.
Change the type of the field speciality in the user table to be able to write down the specialities, separated with commas.
For example 2;3
The problem I got with the second solution is for making foreign keys between my table user and my table specialities, to link them. I may have a bit more difficulties with the PHP in the future too, while wanting to get the specilities for a user (will need to use a parser I guess).
Which solution do you find is the best ?
Thanks.
Absolutely go with your first solution.
Create a third "Many-to-Many" table that allows you to relate a user to multiple specialties. This is the only way to go in your case.
When designing tables, you always want to have each column contain one and only one data element. Think about what querying your second solution would look like. What would you do when you wanted to see all users who had a given specialty?
You might try something like this:
select * from user where specialty like '%2%'
Well, what happens when you have specialties that go to 12? Now "2" matches multiple entities. You could devolve further and try to be tricky, but...you really should just make your data design as normal as possible to avoid all the mess, headache, and errors. Go with Solution 1.
i think the best way is to follow solution1 cause solution2 will end up will lot of complexity later on
I have a question on databases and how information is displayed in regards to Primary and Foreign keys.
For example, there are three tables; Employees, Employee_tickets and Employee_comments.
Each employeecan have multiple tickets and also multiple comments. A foreign key is placed in the Employee tickets and Employee Comments table. My application is built in vb.net with Visual Studio and it is a desktop application. How can I query say.. Employee Name ('Jon Doe') and display all of his tickets in a grid as well as all of the comments people have made on him over time? I have created a View on the sql database which returns all of the information I require but for each ticket listed under ('Jon Doe') the View displays and Employee Name for every single ticket. Is there a way to display the employee name only once and then every ticket listed under that particular individual without displaying the Employee Name again or do I have to make Separate windows to segregate all of this?
This seems like a really dumb question and I cannot for the life of me figure out how to correctly display what is required in this situation.
Here is an example of what I am trying to explain:
So for troy there is one employee name entered in the Employee Names table, There is one CWB ticket entered in the CWB table but there are TWO PQ Cards entered in the PQR Ticket table. How Can I Display only one row for Troy and one Row for his CWB because there are only one of each entered in the tables then the two rows for the PQR Cards under his name?
I have created a view which gathers this information all into the one single view itself then bound the datagridview's to this View.
Your problem has nothing to do with databases. Rather, the issue is that you have an entity (the employee) that has two separate collections associated with it (tickets and comments) and you want to show the contents of both collections.
Doing this in a datagrid is difficult because in its simplest incarnation it's intended to show one collection of like items.
I can think of a number of possibilities:
In your code, convert each collection to a single string value and display that single string value on the row with the employee's name. This conversion could be to comma-separate a stringified version of each item in the collection (as suggested by BS123 in the comments) or could simply be a summary (eg "5 Tickets").
Put the basic employee information in one data grid and then have two additional data grids below it, one bound to the Tickets collection and one to the Comments collection.
Embed data grids directly in the main data grid, one in the Tickets column and one in the Comments column, and bind each one to the appropriate collection in the employee.
Your database structure is correct so don't change that, you simply need to solve the issue of presentation.
What you're missing here is a controller between your view and your model. Your view is presenting exactly what it was given to present - it's up to you to format it.
There are several possible solutions to this, and the correct one partially depends on needs and infrastructure.
If you infrastructure is solid and your needs are near real time, consider dropping separately querying to fill your second and third tables based on what is picked in the first. This will increase the load on the database, but your data will almost always be correct, and the data will come from the database the way you want to see it.
If the database-centered solution is not good for you, LINQ provides some good ways to filter your data into typed collections that would present exactly what you want the user to see.
To get the users:
Dim users = From l In data.lines
Group By FirstName = l.firstName, LastName = l.lastName
Into Tickets = Group, Count()
You can then present this object to your grid. While dynamic typing works here, I think it would be easier to manage view interactions with defined classes. I'll leave that part up to you. Do some searching on LINQ to fill in the rest of the blanks. It's pretty neat stuff.
I am trying to make a database of Users and Movies. Then I want to allow users to click on a movie and mark it as "watched".
What would be the best way to go about structuring this. I mean, could I simply have a table called "Watched" and simply link the UserId to the MovieId in that table to signify that the user has watched that particular movie. This would mean that every instance of a movie being watched will need a record in the table, right? It seems like it could end up taking up ALOT of space in the database.
Is there not an easier way to do this? Sorry if it sounds abit vague. I'm thinking its kind of similar to "friends" on facebook. Would there be a table somewhere where each instance of a friendship occuring is recorded as a record, or is there a way of simply having a list of friends lookup, or something, i don't know... any help much appreciated, thanks!
Your suggestion is correct, using table called "Watched" and simply link the UserId to the MovieId in that table.
In this way, you will have a normalised database, with one-to-many relationship on both sides, toward the "Movies" and "Users" tables.
It will also save you performance cost also when retrieving data later, in case your database becomes a really large one.
You need a user table, movies table, friendship_match table and if you want to record which movie watched at which time, a watch table (with this one you can also display watch history for users)
You have to have a table for friendship because it will contain requests also. If a person adds someone, it doesnt mean the other person will accept it. Other than this, it will take really take a long time if you query the whole users table.
This isn't much of a coding question as opposed to seeking help on going down the right path. So, I have my users set up with username, password, email, posts, & id. The basic forum stuff. But, if I were to add more, say some games in the website that you play and store data with your forum account (being your account for the whole website, in other words), would it be wiser to add those fields to the existing table (i.e.: game1_money) or make another table for each individual side project, then create and link it to each user upon starting the "game" or whatever it is?
If I'm too vague, tell me and I'll try to clarify.
Use separate tables and then a left join when you want the data for the specific game or application. Then if 10% of the users are signed up for the game you don't waste the table space for the other 90%. You also don't need to keep fiddling with the user table.
Anonymous,
Always try to keep your primary table clean and relate everything back to a unique, individual index. In this case, whether you add games, comments, documents, whatever...user User_ID (for example) as the related index field that points back to your main users table.
Here's a good reference on building normalized tables
http://dev.mysql.com/tech-resources/articles/intro-to-normalization.html
Don't store that information in the Users table. Normalise into separate tables.
Create a separate table, say GameSavedInfo, to store this information and reference the users ID from the user table.
I would also create a GameDetails table and use its Id in the GameSavedInfo table.
I need to save a list of user ids who viewed a page, streamed a song and / or downloaded it. What I do with the list is add to it and show it. I don't really need to save more info than that, and I came up with two solutions. Which one is better, or is there an even better solution I missed:
The KISS solution - 1 table with the primary key the song id and a text field for each of the three interactions above (view, download, stream) in which there will be a comma separated list of user ids. Adding to it will be just a concatenation operation.
The "best practice" solution - Have 3 tables with the primary key the song id and a field of user id that did the interaction. Each row has one user id and I could add stuff like date and other stuff.
One thing that makes me lean towards options 2 is that it may be easier to check whether the user has already voted on a song?
tl;dr version - Is it better to use a text field to save arrays as comma separated values, or have each item in the array in a separate table row.
Definitely the 2nd:
You'll be able to scale your application as it grows
It will be less programming language dependent
You'll be able to make queries faster and cleaner
It will be less painful for any other programmer coding / debugging your application later
Additionally, I'd add a new table called "operations" with their ID, so you can add different operations if you need later, storing the operation ID instead of a string on each row ("view", "download", "stream").
It's definitely better to have each item in a separate row. Manipulating text fields has performance disadvantages by itself. But if ever you want to find out which songs user 1234 has viewed/listened to/etc., you'd have to do something like
SELECT * FROM songactions WHERE userlist LIKE '%,1234,%' OR userlist LIKE '1234,%' OR userlist LIKE '%,1234' OR userlist='1234';
It'd be just horribly, horribly painful.