I'm creating a DB for my office. We have about 200 employees. Each employee was required to complete at least 1 of 12 courses within 2 years of being hired (so different completion/qualification dates for every course, some people have been here 20 years, some just 1 year) to become qualified. Some have completed multiple courses. Each course has to be refreshed periodically (each refresh period is different and based on the last refresher date). I'm having trouble with the layout of the table. Here's what I have as an idea, but i'm trying to see if there is a less busy way to lay out the data. I want to be able to run a query that tells me what person has completed what class (so it would have to look at all 3 class columns). I also want to be able to tell when their qualification has lapsed, or is coming up. So far I've created an employee data table that looks like the table below.
ID Name Class1 Class2 Class3 QualDt-Cl1 QualDt-Cl2 QualDt-Cl3 LstRequal1 ...
1 Bob Art Spanish 3/17/1989 9/12/2010 3/8/2012
2 Sally Math 8/31/2012
3 George Physics History 2/6/2005 7/6/1996
4 Casey History 6/8/2000
5 Joe English Sports Physics 12/10/1993 10/15/2001 4/22/2006
The classes are listed in their own table and each class column pulls from that. The qual date refresher will be a calculated column in the query based on the last refresher date.
Is there a way to put all the classes one person is qualified for in one column and have the associated date for requalifiing for each particular cours in another column?
I think it would be less confusing if you had a table per subject and register the people's names under each one with the date passed.
Also it would probably help to declutter the table from uneccssary info like the exact date the exam was passed, you can do month and year or maybe just year? if the lee way is 2 years that would probably make more sense - also making the qulified calculation easier.
The query would work if you searched per subject maybe ? or who would qualify to do what subject this current year and then the next.
this is not much of a question that you would ask on here by the way - but hope the answer helps.
When designing a database, any time you find yourself adding columns with names like Class1, Class2, Class3 you should immediately stop and think about whether it makes more sense to put those columns in a separate child table called Classes with a link (relation) to the parent. There are several reasons for this, including:
What happens when somebody takes a fourth course? Saying "that will never happen" ignores the fact that "never is a very long time" and none of us can predict the future.
When checking whether or not someone has taken a course you really need to check (Class1 IS NULL) OR (Class2 IS NULL) OR (Class3 IS NULL) and that can get really tedious, It also means that if you do have to add Class4 then all of that SQL code has to be corrected.
Similarly, if you want to find someone who took "CPR" you'd have to look for people with (Class1 = 'CPR') OR (Class2 = 'CPR') OR (Class3 = 'CPR'). Yuck.
So, save yourself some trouble (a lot of trouble, really) and create a Classes table:
ID
ClassName
QualDate
(etc. )
...where ID is the ID number from the main table (what is called a "foreign key"). From your sample data, your Classes table would look something like this:
ID ClassName QualDate
1 Art 3/17/1989
1 Spanish 9/12/2010
2 Math 8/31/2012
3 Physics 2/6/2005
3 History 7/6/1996
...
Related
I have two sets of data that are near identical, one set for books, the other for movies.
So we have things such as:
Title
Price
Image
Release Date
Published
etc.
The only difference between the two sets of data is that Books have an ISBN field and Movies has a Budget field.
My question is, even though the data is similar should both be combined into one table or should they be two separate tables?
I've looked on SO at similar questions but am asking because most of the time my application will need to get a single list of both books and movies. It would be rare to get either books or movies. So I would need to lookup two tables for most queries if the data is split into two tables.
Doing this -- cataloging books and movies -- perfectly is the work of several lifetimes. Don't strive for perfection, because you'll likely never get there. Take a look at Worldcat.org for excellent cataloging examples. Just two:
https://www.worldcat.org/title/coco/oclc/1149151811
https://www.worldcat.org/title/designing-data-intensive-applications-the-big-ideas-behind-reliable-scalable-and-maintainable-systems/oclc/1042165662
My suggestion: Add a table called metadata. your titles table should have a one-to-many relationship with your metadata table.
Then, for example, titles might contain
title_id title price release
103 Designing Data-Intensive Applications 34.96 2017
104 Coco 34.12 2107
Then metadata might contain
metadata_id title_id key value
1 103 ISBN-13 978-1449373320
2 103 ISBN-10 1449373320
3 104 budget USD175000000
4 104 EIDR 10.5240/EB14-C407-C74B-C870-B5B6-C
5 104 Sound Designer Barney Jones
Then, if you want to get items with their ISBN-13 values (I'm not familiar with IBAN, but I guess that's the same sort of thing) you do this
SELECT titles.*, isbn13.value isbn13
FROM titles
LEFT JOIN metadata isbn13 ON titles.title_id = metadata.title_id
AND metadata.key='ISBN-13'
This is a good way to go because it's future-proof. If somebody turns up tomorrow and wants, let's say, the name of the most important character in the book or movie, you can add it easily.
The only difference between the two sets of data is that Books have an
IBAN field and Movies has a Budget field.
Are you sure that this difference that you have now will not be
extended to other differences that you may have to take into account
in the future?
Are you sure that you will not have to deal with any other type of
entities (other than books and movies) in the future which will
complicate things?
If the answer in both questions is "Yes" then you could use 1 table.
But if I had to design this, I would keep a separate table for each entity.
If needed, it's easy to combine their data in a View.
What is not easy, is to add or modify columns in a table, even naming them, just to match requirements of 2 or more entities.
You must be very sure about future requests/features for your application.
I can't image what type of books linked with movies you store thus a lot of movies have different titles than books which are based on. Example: 25 films that changed the name.
If you are sure that your data will be persistent and always the same for books and movies then you can create new table for example Productions and there store attributes Title, Price, Image, Release Date, Published. Then you can store foreign keys of Production entity in your tables Books and Movies.
But if any accident happen in the future you will need to rebuild structure or change your assumptions. But anyway it will be easier with entity Production. Then you just create new row with modified values and assign to selected Book or Movie.
Solution with one table for both books and movies is the worst, because if one of the parameters drive away you will add new row and you will have data for first set (real book and non-existing movie) and second set (non-existing book and real movie).
Of course everything is under condition they may be changes in the future. If you are 100% sure, then 1 table is enough solution, but not correct from the database normalization perspective.
I would personally create separate tables for books and movies.
I've got a annoying design issue when designing a database and it's models. Essentially, the database got clients and customers which should be able to make appointments with eachother. The clients should have their availability (on a general week basis) stored in the database, and this needs to be added to the appointment model. The solution does not require or want precise hours for the availability, just one value for each day - ranging from "not available", to "maybe available " to "available". The only solution i've come up with so far includes having all 7 days stored in a row for each client, but it looks nasty.
So here's some of what I got so far:
Client model:
ClientId
Service,
Fee
Customer-that-uses-Client model:
CustomerId
ServiceNeed
Availability-model:
ClientID (FK/PK)
Monday, (int)
...
...
Sunday (int)
And finally, appointment model:
AppointmentId
ClientID
CustomerID
StartDate
Hourse
Problem: is there any way i can redesign the avilability model to ... well, need less fields and still get each day stored with a (1-3) value depending on the clients availability ? Would also be really good if the appointment model wouldnt need to reference all that data from the availability model...
Problem
Answering the narrow question is easy. However, noting the Relational Database tag, there are a few problems in your model, that render it somewhat less than Relational.
Eg. the data content in each logical row needs to be unique. (Uniqueness on the Record id, which is physical, system-generated, and not from the data, cannot provide row uniqueness.) The Primary Key must be "made up from the data", which is of course the only way to make the data row unique.
Eg. values such as Day of availability and AvailabilityType are not constrained, and they need to be.
Relational Data Model
With the issues fixed, the answer looks like this:
Notation
All my data models are rendered in IDEF1X, the Standard for modelling Relational databases since 1993.
My IDEF1X Introduction is essential reading for those who are new to the Relational Model or data modelling.
Content
In the Relational Model, there is a large emphasis on constraining the data, such that the database as a whole contains only valid data.
The only solution i've come up with so far includes having all 7 days stored in a row for each client, but it looks nasty.
Yes. What you had was a repeating attribute (they are named Monday..Sunday, which may not look like a repeating attribute, but it is one, no less than a CSV list). That breaks Codd's Second Normal Form.
The solution is to place the single element in a subordinate table ProviderAvailable.
Day of availability and AvailabilityType are now constrained to a set of values.
The rows in Provider (sorry, the use of "Client" in this context grates on me) and Customer are now unique, due to addition of a Name. The users will not use an internal number to identify such entities, they will use a name, usually a ShortName.
Once the model is tightened up, and all the columns are defined, if Name (not a combination of LastName, FirstName, Initial) is unique, you can eliminate the RecordId, and elevate the Name AK to the PK.
Not Modelled
You have not asked, and I have not modelled these items, but I suspect they will come up as you progress in the development.
A Provider (Client) provides 1 Service. There may be more than 1 in future.
A Customer, seeking 1 Service, can make an Appointment with any Provider (who may or may not provide that Service). You may want to constrain each Appointment to a Provider who provides the sought Service.
As per my comment. It depends on how tight you want this Availability/Reservation system to be. Right now, there is nothing to prevent more than one Customer reserving one Provider on a particular Day, ie. a double-booking.
Normalize that availability table: instead of
ClientID (FK/PK)
Monday, (int)
...
...
Sunday (int)
go with
ClientID (PK/FK)
weekday integer value (0-6 or maybe 1-7) (PK)
availability integer value 1-3
This table has a compound primary key, made of (ClientID, weekday) because each client may have either zero or one entry for each of the seven weekdays.
In this table, you might have these rows:
43 2 3 (on Tuesdays = 2, client 43 is Available =3)
43 3 2 (on Wednesdays = 3, client 43 is MaybeAvailable =2)
If the row is missing, it means the client is unavailable. an availability value of 1 also means that.
I am relatively new to database design so I am still learning a lot. What I am working on is an online time card clock. I am just messing around with it to learn more. My full time job is working for my uncle operating heavy equipment and he has expressed some headaches to me. When going over time cards several employees hand writing is hard to read, several employees don't add the hours correctly so he always has to double check their math, plus some people don't hand in the time sheets on time. Most of the employees have smart phones so my solution is to just make a simple website that has a button for "Clocking in" and "Clocking out" it would also contain several text fields to describe what the employee operated that day and the job site they were on. All of this will be added to a database that will be emailed to the boss at the end of the work week. My question is what would be the best way to setup a database for this? Should I add a separate table for each employee or keep it all in one table? There will be about 20 employees that will use the site. Thanks in advance for any help.
General database principles:
Think about object orientation. Classes of objects.
An "Employee" is one such class, therefore you should have one table that stores employees.
An "Event" such as clocking in or clocking out is a general class of two specific cases, e.g. ClockIn and ClockOut.
You could consider one table to store an Event with a field for the date and time of the event, one field for the employee (a foreign key), one field indicating whether it's in or out
You could alternatively consider one table for ClockIn, one for ClockOut, but this may not be advantageous depending on how you wish to scan the data later when printing reports. I'd personally recommend against this approach, just point out that it's an option.
Ideally, every table should have a numeric primary key
Think of key-value pairs
Employee
1 Jon Doe
2 Juan Gomez
etc...
Event
1 2012-11-29 08:59 Clock In 2
This translates to Juan Gomez clocking in today just before 9am
My question is more of trying to understand what and how I can get something done. Here's the thing:
I got a job to build this application for a school to manage student bio data, work-out and handle student information and basic finance management.
Based on requirements I got from meets with my client, I have an ERD of a proposed MySQL Database with 23 different tables. The one part I would like to understand quickly is displaying data based on school terms. There are 3 terms in a year, each with its own summaries at the end of each term. At the end of 3 terms, a year has gone by and a student is promoted or demoted.
So my question is, how can I render my data to show 3 different terms and also to create a new year working out how to either promote a student or make the student repeat the class its in?
23 different tables? I'd like to see that model.
I don't think you should have one table per term. You'll have to keep adding tables every term, every year.
Sounds like a transcript table should have term and year columns that are incremented or decremented as a student progresses through. It should also have a foreign key relationship with its student: it's a 1:1 between a student and their transcript.
I would have a separate transcript table because I'd prefer keeping it separate from basic personal information about a student. A transcript would refer to the courses taken each term, the grade received for each, and calculate overall progress. If I queried for the transcript for an individual student, I should be able to see every year, every term, every course, every grade in reverse chronological order.
I have a mysql table with users and their weekly calendar.
Every user can set his own availability for the week (morning, afternoon, night / MON thru SAT), and that is not going to change often, almost never.
Imagine those users are personal trainers in a gym, or tennis courts you can book...
My problem here is to find the right query (or maybe even rethinking the way i'm storing that data in mysql) in order for an external web user to check availability of them based on 3 check buttons [o]morning, [o]afternoon, and [o]night
So I want my web user to go to my website and check/uncheck those buttons in order to see which one (personal trainer, or whatever) is available
So if I check Morning i can see only the people available, also (but not only), in the morning,(because a personal trainer can be available during the morning but also in the afternoon etc..)..
it may sounds an easy problem but i'm having hard time...
any help is appreciated
Thanks!
This isn't really an algorithm question, this is more of a DBA question. You'd most likely have a user table and an availability table.
user:
userid
...
availability:
userid
day
timeofday
When given a query such as Monday Wednesday Morning Afternoon (assuming the relationship is (Monday OR Wednesday) AND (Morning OR Afternoon)) you can do a query such as.
SELECT userid FROM availability WHERE day='wednesday' OR day is 'monday' AND timeofday='morning' OR timeofday='afternoon'
The answer to this question will be dependant on your DB structure. If your are storing the availabile times as 1, 2, 3 or any combo of such 12, 13, 123, 23 then you can simply use a
MYSQL Regular expression to limit your results based on the input checkbox criteria.
I would suggest somthing like:
SELECT trainer FROM trainer_table WHERE availaility regexp '[Limiting Criteria]'
In the above code, simply replace trainer with the name of your fields you wish to return. Then replace trainer_table with the name of your table and finally replace Limiting Criteria with your limiting text, be it 1 or 2 or 3 or any combination.
If you want more specific help, an example of your own table structure would be helpful.