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.
Related
I am going to create a table with fields like ID, Name, Email ID, Phone, Designation, Department and Institute. In this regard, I believe making the fields like Designation, Department and Institute as foreign key is an efficient one (as it have redundant values). Am I correct? or suggest some better ideas.
Yes you are correct, redundancy is one of the things you should avoid. And i encourage you to read more about normalization because you will find more things that will not only make your database more efficient, but easier to use / understand when it grows and gets complicated.
And as the example in the reply above, you should also pay attention to the tables / columns names.
So instead of
Designation, Department and Institute as foreign key
You should follow a pattern and name them like table name + id, so you know just by looking at it that it is a foreign key and it's referencing that table.
I’m trying to create a relational database whereby I can award students ‘Awards’ throughout their time at school. I have chosen mySQL to do this and have a system ready as soon as I have sorted the database out properly.
I think I have these tables correct, however I’m not sure which would be the primary/foreign/indexes (if they are even needed)
I will have 10 Awards that I will award, and one student could earn all ten over their time at the school.
Am I correct in thinking the tables should look something like this:
Student
StudentID
FirstName
Surname
SchoolYear
Form
Awards
AwardID
AwardTitle
AwardDescription
How would I “link” these together on MySQL properly? So that I can assign multiple awards to students?
Many thanks in advance.
The best approach here would be to make a 'link' table, lets say AwardedStudents and within it to have:
AwardRowID PK
,StudendID FK reference Student(StudentID)
,AwardID FK reference Awards(AwardID)
So later on, you are going to be able to join on both criteria
EDIT: You can omit the AwardRowID column if there is no way one student to be awarded with the same AwardID (because this will lead to duplicating rows) and simply make composite PK from StudendID and AwardID. But if this is possible situation, you need to stay with the AwardRowID PK in the table.
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.
I am trying to determine how the tables need to be linked in which ways.
The employees tables is directly linked to a number of tables which provide more information. A few of those tables have even more details.
Employees have a unique employeeid but I understand best practice is to still have a id?
Customers have a unique customerid
Employees have a manager
Managers are employees
Customers have a manager associated with them. manager associated with them
Employees may have a academic, certification and/or professional information.
With all of this said what would be the best recommendation for creating primary and foreign keys? Is there a better way to handle the design?
EDIT
Updated diagram to reflect feedback thus far. See comments to understand changes taking place.
Though your question is sensible, before you go any further in design, I would suggest for you to spend some time understanding relationships, foreign keys and how they propagate through relationships.
The diagram is utterly wrong. It will help it you start naming primary keys with full name, TableNameID, like EmployeeID; then it will become obvious how keys propagate through relationships. If you had full names you would have noticed that all your arrows are pointing in the wrong direction; parent and child are reversed. Anyway, takes some practice. So I would suggest that you rework the diagram and post the new version, so that we can comment on that one. It should start looking something like this (just a small segment)
EDIT
This is supposed to point you to towards the next step. See if you can read description (specification) and follow the diagram at the same time.
Each employee has one manager, a manager manages many employees.
A manager is an employee.
Each customer is managed by an employee who acts as an account manager for that customer.
Account manages for a customer may change over time.
Each employee is a member of one team, each team has many employees.
Employee performance for each employee is tracked over time.
Employee may have many credentials, each credential belongs to one employee only.
Credential is academic or professional.
Employees have unique employeeID but I understand best practice is to
still have a id?
No. (But keep reading.) You need an id number in two cases: 1) when you don't have any other way to identify an entity, and 2) when you're trying to improve join performance. And that doesn't always work. ID numbers always require more joins, but when the critical information is carried in human-readable codes or in natural keys, you don't need a join to get to it. Also, routine use of ID numbers often introduces data integrity problems, because unique constraints on natural keys are often omitted. For example, USPS postal codes for state names are unique, but tables that use ID numbers instead of USPS postal codes often omit the unique constraint on that two-character column. In your case, you need a unique constraint on employee number regardless. (But keep reading.)
Employees have a manager.
Does the table "team" implement this requirement? If the "manager" table identifies managers, then your other manager columns should reference "manager". (In this diagram, that's customers, team, and customer_orders.)
Managers are employees.
And that information is stored in the table "manager"?
Customers have a manager associated with them.
And so does each order. Did you mean to do that?
Employees may have a academic, certification and/or professional
information.
But apparently you can't record any of that information unless you store a skill first. That doesn't sound like a good approach. Give it some more thought.
Whenever you design tables with overlapping predicates (overlapping meanings), you need to stop and sit on your hands for a few minutes. In this case, the predicates of the tables "employees" and "customers" overlap.
If employees can be customers, which is the case for almost every business, then you have set the stage for update anomalies. An employee's last name changes. Clearly, you must update "employees". But do you have to update "customers" too? How do you know? You can't really tell, because those two tables have independent id numbers.
An informal rule of thumb: if any real-world entity has more than one primary key identifying it in your database, you have a problem. In this case, an employee who is also a customer would have two independent primary keys identifying that person--an employee id and a customer id.
Consider adding a table of persons, some of whom will be employees, and some of whom will be customers. If your database is well-designed and useful, I'll bet that later some of the persons will be prospects, some will be job applicants, and so on. You will need an id number for persons, because in the most general case all you can count on knowing is their name.
At some point, you'll have to take your database design knowledge to the next level. For an early start, read this article on people's names.
i wanna have a Users details stored in the database.. with columns like firstname, last name, username, password, email, cellphone number, activation codes, gender, birthday, occupation, and a few other more. is it good to store all of these on the same table or should i split it between two users and profile ?
If those are attributes of a User (and they are 1-1) then they belong in the user table.
You would only normally split if there were many columns; then you might create another table in a 1-1 mapping.
Another table is obviously required if there are many profile rows per user.
One table should be good enough.
Two tables or more generally vertical portioning comes in when you want to scale out. So you split your tables in multiple tables where usually the partiotioning criteria is the usage i.e., the most common attributes which are used together are housed in one table and others in another table.
One table should be okay. I'd be storing a hash in the password column.
I suggest you read this article on Wikipedia. about database normalization.
It describes the different possibilities and the pros and cons of each. It really depends on what else you want to store and the relationship between the user and its properties.
Ideally one table should be used. If the number of columns becomes harder to manage only then you should move them to another table. In that case, ideally, the two tables should have a one-one relationship which you can easily establish by setting the foreign key in the related table as the primary key:
User
-------------------------------
UserID INT NOT NULL PRIMARY KEY
UserProfile
-------------------------------------------------------
UserID INT NOT NULL PRIMARY KEY REFERENCES User(UserID)
Depend on what kind of application it is, it might be different.
for an enterprise application that my users are the employees as well, I would suggest two tables.
tbl_UserPersonallInformation
(contains the personal information
like name, address, email,...)
tbl_UserSystemInformation (contains
other information like ( Title,
JoinedTheCompanyOn,
LeftTheCompanyOn)
In systems such as "Document Managements" , "Project Information Managements",... this might be necessary.
for example in a company the employees might leave and rejoin after few years and even they will have different job title. The employee had have some activities and records with his old title and he will have some more with the new one. So it should be recorded in the system that with which title (authority) he had done some stuff.