Look at street tables with the "1" and "2" files. MapInfo came up with a
view scheme that is useful for tables where one of the fields has many
duplicate entries - like street files. A street table may have 100,000
segments, but only 10,000 street names. By having two tables, one with all
of the unique street names along with a unique integer (and not mappable)
and one with all of the segments and unique field info (like address range
for each segment) and a street id, the disk space required can be
significantly less. Here's an illustration.
!Table
!Version 100
Open Table "CHGOS1" Hide
Open Table "CHGOS2" Hide
Create View COMBO As
Select Street,FromLeft,ToLeft,FromRight,ToRight,Class,Tiger_Refnum
>From CHGOS2, CHGOS1
Where CHGOS2.MI_refnum=CHGOS1.MI_refnum
CHGOS1 looks like (310,759 records)....
FromLeft ToLeft FromRight ToRight Class MI_refnum
2501 2749 2500 2748 A40 1
0 0 2000 2104 A40 2
0 0 0 0 A40 3
13 7 18 8 A01 4
5 1 6 2 A01 4
...
CHGOS2 looks like (33,582 records)...
Street MI_refnum
Oak Av 1
Devon Av 2
Longmeadow Dr 3
Fernwood Ln 4
Bateman Rd 5
Longmeadow Ct 6
Penny Rd 7
W Dundee Rd 8
...
...so, as long as there is a field to join on, the view will work. Note
that the Create View statement is undocumented.
With disk space cheap, I'm not so sure the create view for street files is
useful anymore.
I don't see any problems with the statement generically; it's been around
since Version 1 of MapInfo for Windows. Things like the "i" tool work fine.
Table appends are a no-no, though.
I hope this helps.
Alex Machinis
EMPOWER GEOGRAPHICS, INC.
1000 Executive Way
Des Plaines, Illinois 60018-1502
847/299-6952 x212 Fax: 847/299-6990
http://www.empowergeo.com
mailto:[EMAIL PROTECTED]
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-----Original Message-----
From: Steve Wallace [mailto:[EMAIL PROTECTED]]
Sent: Friday, February 12, 1999 11:47 AM
To: [EMAIL PROTECTED]
Subject: MI How to create view?
I thought I remembered seeing a post about making *.TAB files that were
actually queries of other files. I would like to have a MapInfo TAB file
that is actually just a dynamic sub-set of a larger table.
While this is possible with other database programs, I have not figured out
how to do it with MapInfo.
Suggestions appreciated!
Steve Wallace
GIS & Market Information Manager
Florida Farm Bureau Insurance Companies
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