Are Table Relationships necessary?

  • Thread starter Thread starter A Future Computer Scientist
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A Future Computer Scientist

My question table relationships in the database . Is it necessary to have
two or more tables related to one another if there isn't a "seeable"
relationship? . Even though all of the tables have redundant fields, which
are needed, I just don't see any 100% relationship with any field to really
joining any two tables. When I went back and actually thought about the
relationships I had setup, I actually tried to redo the relationships with
certain tables, but it's just making me kinda crazy.
 
A Future Computer Scientist said:
My question table relationships in the database . Is it necessary to have
two or more tables related to one another if there isn't a "seeable"
relationship? . Even though all of the tables have redundant fields, which
are needed, I just don't see any 100% relationship with any field to really
joining any two tables. When I went back and actually thought about the
relationships I had setup, I actually tried to redo the relationships with
certain tables, but it's just making me kinda crazy.
Click to expand...

Redundant fields are *never* needed in a relational database. It breaks one
of the fundamental rules and will almost always make things much more
difficult to maintain and manage.
If you understand the relational model and know why breaking the rule may
cause a lot of problems you may do so at your own risk.

Even simple violations can cause problems. HomePhone, businessPhone was good
enough for many years. Then people got cell phones.
So you add that field, modify two dozen forms and 12 reports.
Then they got pagers, cabins in the woods, girl friends and alternative work
sites.
So you add that field, modify two dozen forms and 11 reports and the boss
got the one you missed and really needed to find the guy but he was at his
cabin in the woods.
 
I agree with Mike. Inclusion of redundant fields is almost always the result
of non-normalized table design, which is just asking for trouble down the
road. I'd suggest a brush-up on relational database design and theory ...
there are several good books regarding this issue, Google on "relational
database books" or something like that to get recommendations ...
 
So, it's not always what the users need that's must important? I know
redundant data isn't good design. But the users want the redundancy. If I
strip down all of the redundant data in each table, then the basic fields
for each table are met.

It's racking my brain because designing the database is a one person job(Me)
and I have no help. And the users of the database aren't in a
computer-related field. But you're right, I can use some more info on
designing. I'm basically picking it up as I go along because this is my
first real, professional database design.
 
A Future Computer Scientist said:
So, it's not always what the users need that's must important? I know
redundant data isn't good design. But the users want the redundancy. If I
strip down all of the redundant data in each table, then the basic fields
for each table are met.

It's racking my brain because designing the database is a one person job(Me)
and I have no help. And the users of the database aren't in a
computer-related field. But you're right, I can use some more info on
designing. I'm basically picking it up as I go along because this is my
first real, professional database design.
Click to expand...

What the user needs and wants are frequently two different things.
I would (and have) explained that what they want will usually cost then
more to start and *will* cost them more down the road.
In many cases they could learn to do simple reports with a properly designed
system but have to pay me to write code to produce what they want.

I tell them in writing and get them to sign something indicating that this
is what they want and may not be what they need.
I also make it clear that I do not do the next job until I get paid for the
last one.
 
Mike Painter said:
Even simple violations can cause problems. HomePhone, businessPhone was good
enough for many years. Then people got cell phones.
So you add that field, modify two dozen forms and 12 reports.
Then they got pagers, cabins in the woods, girl friends and alternative work
sites.
So you add that field, modify two dozen forms and 11 reports and the boss
got the one you missed and really needed to find the guy but he was at his
cabin in the woods.
Click to expand...

Very nice explanation. Thanks.

Tony

--
Tony Toews, Microsoft Access MVP
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read the entire thread of messages.
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http://www.granite.ab.ca/accsmstr.htm
 
Yeah, I know what you mean. Well, I went in and took out the redundant data
and when I redid the table relationships, they all came out perfect. I even
got a few that were one-to-one, which worked even better for those tables.

And with the removiing of the redundant data has helped in other ways. I
created an user interface in Visual Basic. So Now, I can implement some
things I've been thinking about plus I can better setup the interface.
 
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