Eddie Said:

can anyone help me with this entity relationship diagram and how it should be done?

We Answered:

You have the tables or Entities so you are half way there, you just need to read the case study and try to visualise what belongs where, the general rule of thumb is that repeating items would be a seperate entity and a key would link the items to another entity, for example, in the above you have an employee who attends many courses. in laymans terms you wouldnt do this

Employee Name Andy Smith,
Employee TelNo 012772322222,
Employee Department B26,
course A details

Employee Andy Smith,
Employee TelNo 012772322222,
Employee Department B26,
course B details

its much more efficiant to store the employee details once and have a key that links the course details with that employee e.g.

Employee Id,
Employee Andy Smith,
Employee TelNo 012772322222

then:

Employee Id
Course A details

Employee Id,
Course B Details

this way you are not repeating information you can use the employees key to get their course details. (hope your following this)

reading the above we know what to store against an employee

"For each employee we record his/her name, department, department head, internal telephone number and the date and description of courses attended"

REMEMBER an employee can attend more than one course so we would not store the course details in the employee entity, we need some id that would link the courses to an employee, so we would generally give each employee a unique or Primary key, so the employee entity looks like:

Employee {EmployeeId, Name}

Notice I didnt include Department or department head or internal telephone in there either. Again if you think about it, chances are that more than one employee would have the same department e.g.

Employee Entity A, department A, department head a, department internal telephone

Employee Entity B, department A, department head a, department internal telephone

so if you department changed their telephone number, guess what, you have to go through each employee and change all of those details. so what do we do, simple, we do the same as the courses and put the department in a seperate entity and link them with an id. So we would now have :

Employee {EmployeeId, Name, DepartmentId}
Department {DepartmentId, Department, Department Head, Internal Telephone Number}

hope your seeing a pattern here. Department has a unique id which is stored against an employee which wouldnt change so if we go back to our previous scenario, we woudl do this :

Employee Entity A, DepartmentId
Employee Entity B, DepartmentId

this way as long as the id stays the same the department details can be updated in the department entity and the employee entity can remain the same ( i am assuming that an employee belongs to just one department) .

so lets take the rest of the case study and it would look something like :

Employee (EmployeeId, Name, DepartmentId}

EmployeeId is a primary key as it uniquely identifies an employee, no two employees have the same id.

** I would have an relationship entity which stores the courses an employee has been on which would be:

Employee Courses {EmployeeId, CourseId}

EmployeeId and CourseId are foreign keys to the employee and course entites respectively.

Department {DepartmentId, Department Head, Internal Tel No}
DepartmentId is a primary key

Course {CourseId, Course Name}
CourseId is a primary key

course comprises of skills so :

Skills {CourseId, Skill Description}

CourseId is a foreign key to the courses entity, again you could have a courseskills entity as not to repeat skills as two course may have the same skills so you would need to create a CourseSkills entity but thats another entity not mentioned.

Instructor {InstructorId, name, DepartmentId}
Instructor here is the primary key and Departmentid is a foreignkey poiting to the department an instructor belongs

RunOfACourse {CourseId, Date Started, InstructorId}

Course Id in this entity is a foreign key to the course entity we know that a course lasts for six weeks so this could be calculated from the start date, if this would not always be the case, I would put an end date in too. Instructor id is a foreign key pointing to which instructor is running this run of the course. remember that different instructors may run the same course at different dates.

Hope that helps.

Martin Said:

How do you feel about this?

We Answered:

'Randomness' is found everywhere, and it could be said it is the 'spice of life.' Without 'randomness' the world would be far too predictable and boring...... like your very long post. lol. Seriously... j/k. ;-)

Anita Said:

Economics Problem ... ready the question carefully and answer them?

We Answered:

Case # 2

12- B
13- C
14- A
15- C

Virginia Said:

Would you approve this method of reducing the voting power of morons?

We Answered:

I do wish that only truly intelligent people were allowed to vote, but unfortunately, there are millions of idiots out there who would vote against that proposition! I think people who have an average or higher IQ are far outnumbered by the ones who can't form a coherent thought. All you have to do to be convinced of that is read about 75% of what gets posted to this section.

And to the guy below me, LOOK pal. I'm sorry but there is definitely a very direct correlation between your capacity for comprehension and problem solving and your ability to make sound judgements!!!

Lauren Said:

The consensus is wrong on global warming. Wonder when the New York Times will figure it out?

We Answered:

Sounds like this Lomborg book is a good read, I may have to pick it up. It beats someone who's been a proven liar. At least he addresses the other side's issues too, which is important. Global Warming fanatics will get nowhere if they don't attempt to rationally appease policy makers and instead demand a rollback on progress.