I know the title looks a little faque, but my technical english is not as good as would it to be.
My question. I'm designing a kind of work order form with access database. The pretty standard database I can manage, but my problems starts when I want multiple entries for one customer.
For example:
Customer Chris with Id 1 has a problem, he has a BSOD which is fixed. Customer Chris has a new problem some weeks later with his videocard, which will be fixed later ofcourse (;-))
The info above needs to be stored in the access database. Do I need a second table? I really don't have a idea.
You need at least two tables, one for customers and one for problems. The problem table should include such information as customer id, date fixed and fix applied. You may also want to include the engineer, in which case you will also need an employees table, and so it grows.
You may wish to read http://r937.com/relational.html
Related
I'm a little stumped on whether i can make this process of changing addresses easier. I'll explain the situation:
Basically I have three entities, Students, Addresses, StudentsAddresses. Students have many addresses, since they can change alot and rapidly (especially foster kids / homeless kids). So ill be changing them a lot. However based on each address I Want a user to attach (enter it via the UI) the price it would cost to pick that student up via bus service. So my initial thought was, ok, let me attach a column onto my join table 'StudentsAddresses' called 'dailyPrice', this is the cost for each day a student is picked up, and another column called 'adjustmentPrice', which is an additional cost for whatever special circumstance that requires extra work to pick up a student. Is my thinking going to cause me problems the more students I have in the future? Will it get harder to manage?
Another option I thought about, was creating a new Table called Pricing. And another join-type table called StudentsAddressesPricing
StudentsAddressPricing has three columns,
studentId
addressId
pricingId
each field connects the three together. So if i ever needed Students, with their addresses, and the pricing, i would query this table and eager load Students, Addresses, and Pricing. Does this approach seem much cleaner since i've abstracted pricing out a bit? Trying to determine the best way to go about this without having to many headaches in the future incase I wan't to add more attributes pricing related, or address related.
And then I even thought, hey what if pricing is just different for one day? How would I even consider that. Would I need a different kind of entity to handle that? Is doing alot of joins going to hurt my application performance?
Just looking for some insight on how others would do it, and criticism on why im off the ball.
The main question you should ask yourself is: on what does the price depend?
If the price is determined by the address, you might as well add it to addresses. If the price also depends on the student (e.g., depending on their financial situation), it would make sense to put it into studentsaddresses.
In other words: The table where the price is stored should have foreign keys to everything outside the table that determines the price. If that makes it fit into one of the existing tables, keep it there.
I'm writing an application to allow users to create a Poll. They ask a question and set n number of predefined answers to the question. Other users can vote on the answers provided for that question.
Current structure
I have designed the database like this:
Storing the vote count
Current thinking is, I create a new column called vote_count on the link table and every time that answer gets voted, it updates the record.
This works. But is it right? I'm new to database systems, so I can't imagine I'm doing much right. What are some more efficient ways to achieve this?
As far as it goes yes that's OK. However these tables will be incomplete. When your second quiz is created, you'll have to extend the QUESTIONS table. If this second quiz's Q1 also has a yes/no answer, you're going to have to extend the LINK/VOTES table.
You also have to think about how it's going to be queried and design indexes to support those queries.
Cheers -
I currently have two tables. One is accounts and one is tbl_units_info. My boss wants me to make it so that accounts are restricted from reading certain rows in a table. Frankly, I think my boss has no idea what he is talking about, but I'm hoping someone here can prove me wrong.
For example, accountname krikara can only view the entries of the tbl_units_info table where the TBID column is 0909.
Is this even possible? To make krikara only able to view the rows in that table where column TBID = 0909?
It can not be implemented plainly on DBMS level since SELECT privilege has table level. You can not restrict rows reading. And this is good, I think - because data could be changed, so in general there is no solid condition for rows restriction (and, therefore, there could not be valid implementation for that on DBMS level).
You can, however, use VIEW - but it is a middlepoint, not common solution (I still not think it will help with tracking rows changes, but may be I'm wrong due to your application logic)
You can try to implement it in your application, but it still has problem I've described above: in table, data is changing. You'll probably have troubles with tracking all changes. I think you can separate your rows on two (several) tables and then build your permissions model. But - if some basically similar entities must have different permissions - probably you should reconsider application security model?
You could solve it by giving accounts just the reading rights to a view instead of the whole table.
CREATE VIEW `tbl_units_info_krikara` AS
SELECT * FROM `tbl_units_ino` WHERE `TBID`='0909';
And then assign the respective rights to your user.
MySQL CREATE VIEW documentation
I am making a database that is for employee scheduling. I am, for the first time ever, making a relational mySQL database so that I can efficiently manage all of the data. I have been using the mySQL Workbench program to help me visualize how this is going to go. Here is what I have so far:
What I have pictured in my head is that, based on the drawing, I would set the schedule in the schedule table which uses references from the other tables as shown. Then when I need to display this schedule, I would pull everything from the schedule table. Whenever I've worked with a database in the past, it hasn't been of the normalized type, so I would just enter the data into one table and then pull the data out from that one table. Now that I'm tackling a much larger project I am sure that having all of the tables split (normalized) like this is the way to go, but I'm having trouble seeing how everything comes together in the end. I have a feeling it doesn't work the way I have it pictured, #grossvogel pointed out what I believe to be something critical to making this all work and that is to use the join function to pull the data.
The reason I started with a relational database was so that if I made a change to (for example) the shift table and instead of record 1 being "AM" I wanted it to be "Morning", it would then automatically change the relevant sections through the cascade option.
The reason I'm posting this here is because I am hoping someone can help fill in the blanks and to point me in the right direction so I don't spend a lot of hours only to find out I made a wrong turn at the beginning.
Maybe the piece you're missing is the idea of using a query with joins to pull in data from multiple tables. For instance (just incorporating a couple of your tables):
SELECT Dept_Name, Emp_Name, Stat_Name ...
FROM schedule
INNER JOIN departments on schedule.Dept_ID = departments.Dept_ID
INNER JOIN employees on schedule.Emp_ID = employees.Emp_ID
INNER JOIN status on schedule.Stat_ID = status.Stat_ID
...
where ....
Note also that a schedule table that contains all of the information needed to be displayed on the final page is not in the spirit of relational data modeling. You want each table to model some entity in your application, so it might be more appropriate to rename schedule to something like shifts if each row represents a shift. (I usually use singular names for tables, but there are multiple perspectives there.)
This is, frankly, a very difficult question to answer because you could get a million different answers, each with their own merits. I'd suggest you take a look at these (there are probably better links out there too, these just seemed like good points to note) :
http://www.devshed.com/c/a/MySQL/Designing-a-MySQL-Database-Tips-and-Techniques/
http://en.wikipedia.org/wiki/Boyce%E2%80%93Codd_normal_form
http://www.sitepoint.com/forums/showthread.php?66342-SQL-and-RDBMS-Database-Design-DO-s-and-DON-Ts
I'd also suggest you try explaining what it is you want to achieve in more detail rather than just post the table structure and let us try to figure out what you meant by what you've done.
Often by trying to explain something verbally you may come to the realisations you need without anyone else's input at all!
One thing I will mention is that you don't have to denormalise a table to report certain values together, you should be considering views for that kind of thing...
currently Im working on a project that, at first glance, will require many tables in a database. Most of the tables are fairly straightforward however I do have an issue. One of the tables will be a list of members for the website, things like username, password, contact info, bio, education, etc will be included. This is a simple design, however, there is also a need for each member to have their availability entered and store in the database as well. Availability is defined as a date and time range. Like available on 4/5/2011 from 1pm to 6pm EST, or NOT available every friday after 8pm EST. For a single user, this could be a table on its own, but for many users, Im not sure how to go about organizing the data in a manageable fashion. First thought would be to have code to create a table for each user, but that could mean alot of tables in the database in addition to the few I have for other site functions. Logically i could use the username appended to Avail_ or something for the table name ie: Avail_UserBob and then query that as needed. But im curious if anyone can think of a better option than having the potential of hundreds of tables in a single database.
edit
So general agreement would be to have a table for members, unique key being ID for instance. Then have a second table for availability (date, start time, end time, boolean for available or not, and id of member this applies to). Django might sound nice and work well, but i dont have the time to spend learning another framework while working on this project. The 2 table method seems plausable but Im worried about the extra coding required for features that will utilize the availability times to A) build a calender like page to add, edit, or remove entered values, and B) match availabilities with entries from another table that lists games. While I might have more coding, I can live with that as long as the database is sound, functional, and not so messy. Thanks for the input guys.
Not to sound like a troll, but you should take a look into using a web framework to build most of this for you. I'd suggest taking a look at Django. With it you can define the type of fields you wish to store (and how they relate) and Django builds all the SQL statements to make it so. You get a nice admin interface for free so staff can login and add/edit/etc.
You also don't have to worry about building the login/auth/change password, etc. forms. all that session stuff is taken care of by Django. You get to focus on what makes your project/app unique.
And it allow you to build your project really, really fast.
djangoproject.org
I don't have any other framework suggestions that meet your needs. I do... but I think Django will fit the bill.
Create a table to store users. Use its primary key as foreign key in other tables.
The databases are written to hold many many rows in a table. There are not optimized for table creation. So it is not a good idea to create a new table for each user. Instead give each user an unique identifier and put the availability in a separate table. Provide an additional flag to make an entry valid or invalid.
Create a table of users; then create a table of availabilities per user. Don't try to cram availabilities into the user table: that will guarantee giant grief for you later on; and you'll find you have to create an availabilities table then.
Google database normalization to get an idea why.
Take it as truth from one who has suffered such self-inflicted grief :-)