Figuring out the entity relationships

Tekk · October 18th, 2003, 02:21 AM

Well Im trying to figure out the final many:many relationship between the entities I have here. I talked to my teacher and she gave me a real vague clue (I didn't want the answer at all but she basically told me something that I already knew...no help at all). So I have 7 entities and the project says there is 8 total. What Im trying to figure out is which of the two would it be? I have narrowed it down between the room/service entities or the employee/service_performed entities. What Im also wondering is if there can even be a many:many relationship between a normal entity and an event entity (which is what the employee/service_performed relationship is consider s_p is an event)?

Damn logic of this stuff sometimes confuses me. If someone has an idea then that'd be awesome. Thanks a bunch. Maybe give me ideas to head in the right direction...

Tekk

Tekk · October 18th, 2003, 02:30 AM

oops...here's the pic of the diagram

John Prophet · October 18th, 2003, 02:32 AM

"The Entity"?? I thought maybe Prince had a new name or something.

JP

vass0922 · October 18th, 2003, 02:33 AM

hmm not sure about a employee/service relationship...

I understand many:many relationships just fine..

Class:students is a many to many

Each student can have many classes, and each class has many students

Can you give some examples on the employee/service?

Hmm maybe a room offers many services, and each service is offered in many rooms?

Tekk · October 18th, 2003, 02:36 AM

Each employee can perform many services, and each service can be performed by many employees.

For example, an employee can have multiple services to do (clean a room, wash the laundry, etc) while each service can be done by many different employees (Jack can clean a room and then later Bob can clean another room).

Tekk · October 18th, 2003, 02:40 AM

Of course, the project also lists the attributes for each entity and one of the listed attributes for employee is "Employee_Job_Code" which can lead one to believe that each employee really does only have one specific job and no other, which would change the relationship

vass0922 · October 18th, 2003, 03:26 AM

not necessarily

If his job code is 'sanitation engineer' he could perform many services

It depends on the definition of the attribute

Tekk · October 18th, 2003, 04:11 AM

True...nevermind on that. Makes too much sense that each employee can do multiple jobs.

vass0922 · October 18th, 2003, 04:59 AM

well.. then there are those OTHER employees.. they can take a smoke break.. go to the bathroom.. smoke break.. lunch

there still something you need or confused about?

Tekk · October 18th, 2003, 05:10 AM

This is what I have so far.....should the Room_Services be changed to an event such as Room_Serviced? Plus whether or not that is an even, Im a little confused on whether the relationships need to be identifying or non-identifying. Would leaving those correlative entities with just 2 keys be ok? (considering we're not supposed to add attributes unless its too an event where we could only add a counter key XXXX_Number)