New normalised table design question

L

Liz James

Have reorganised tables with help from this discussion group.
3 tables:
tblTrackRecs
tblParameters
tblValue

Most parameters are at a fixed point on a track, recorded by a chainage and
a waypoint. Another type of parameter, section of track, has start chainage
and end chainage and a totally different set of attributes from fixed point
parameters.

Should I put the Section type of parameter and its attributes into a new
table so that I can have two forms open at same time when recording details
along a track. Details at a fixed point are easy, do one and then a new
record for the next one. A section end is only recognised when a significant
change to the current section’s attributes occurs.

Sections are more difficult because this form needs to stay open on the
current record until the end of section is reached, by which time several
fixed point records have been recorded and saved.

Has anyone been here before and knows the pitfalls of having all in one
table or two tables?
 
J

John Vinson

Have reorganised tables with help from this discussion group.
3 tables:
tblTrackRecs
tblParameters
tblValue

Most parameters are at a fixed point on a track, recorded by a chainage and
a waypoint. Another type of parameter, section of track, has start chainage
and end chainage and a totally different set of attributes from fixed point
parameters.
Click to expand...

I'm not sure I am completely understanding the referents here. Is this
a survey line? What's "chainage" - a unit of distance? What's a
"waypoint"? I just think I may be able to give better advice if I
understand the jargon a bit better!
Should I put the Section type of parameter and its attributes into a new
table so that I can have two forms open at same time when recording details
along a track. Details at a fixed point are easy, do one and then a new
record for the next one. A section end is only recognised when a significant
change to the current section’s attributes occurs.
Click to expand...
Sections are more difficult because this form needs to stay open on the
current record until the end of section is reached, by which time several
fixed point records have been recorded and saved.
Click to expand...

If you have a one to many relationship between Sections and fixed
points, you should really consider using a Form with a Subform rather
than having two independently open Forms.
Has anyone been here before and knows the pitfalls of having all in one
table or two tables?
Click to expand...

The basic principle is that each Table should represent one distinct
kind of Entity: a real-life person, event, or thing. In this case, you
seem to have things that are made up of finer-detail things (trac
records and points). Each trackrecord consists of many points; each
point belongs to one and only one trackrecord (for the purposes of
that trackrecord, at least); so you have two tables in a one to many
relationship.

John W. Vinson[MVP]
 
L

Liz James

Thanks, I will rephrase the question.
How robust will it be for a database, running on computers with runtime only
installed, to have 2 forms open at the same time to update data for the same
table.
 
J

John Vinson

Thanks, I will rephrase the question.
How robust will it be for a database, running on computers with runtime only
installed, to have 2 forms open at the same time to update data for the same
table.
Click to expand...

It will give the user error messages when they attempt to update the
same record from both forms. A form/subform would be safer.

John W. Vinson[MVP]
 
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