----- Original Message -----
From: Petr Grinshpun <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, July 06, 2000 4:35 PM
Subject: MI Remove dups
> Hi mappers,
> Does anybody know how to remove duplicate records from a mappable table
> and get a mappable resulting table.
> Any idea would be greatly appreciated.
> Thank you.
> Petr Grinshpun,
> Senior System Analyst,
> LDS, Inc.
> 703-741-7094
You can't begin to do this until you define what a "duplicate record" in a
"mappable table" is.
Do you mean:
1) points lying at the same location?
2) a field that is supposed to have a unique value for each record, but the
table has multiple records with the same value?
3) more complicated objects that are coterminous?
4) several records exist representing disjoint parts of a polygon that is
supposed to be one record?
The first two can be accomplished fairly easily, the third is rather
difficult without involving topology.
To accomplish the first two,
a. Add two "float" columns to your table, called "X" and "Y" (you may
already have them).
b. Using two invocations of Table -> Update Column, update the "X" column
with CentroidX(obj), and the Y column with CentroidY(obj).
c. Use Query -> SQL Select to make a table with a unique values. Put each
column that is supposed to have a unique value in the "group by" area of the
dialog box. If you're grouping points lying at the same location, put the
"X" and "Y" columns you created in the "group by" area.
d. Save the table that results (File -> Save As). Close the selection table.
e. Open the table you saved in step d. Use Table -> Create Points to
re-create the point objects.
Hope this helps,
Spencer
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