There is one important rule (from my experience) to remember when using views :
the mappable table must be the last table in the join.
If you get this the wrong way round it will join by Row-Ids only!
Also note that (from my experience) a view always shows all the map objects on a map
and in a browser, but only the records that qualify (ie meet the join condition) will
appear to have data. The rest will appear as blank grey lines in a browser and without
any info attached in a mapper.
The syntax for creating views is as follows:
Create view "myView" as
<Select statement without an into or grouping clause>
They seem to work quite well within Tab files, I would suggest using the same name for
the view as the name of the TAB file.
I believe that views are an undocumented feature, so it is always worth checking the
behaviour with each version of MapInfo. But the last time I checked you could join up
to 9 tables, and they are suitable for 1:1 and 1:Many joins - provided the map object
only appears once.
I hope this helps
Carl Nunn
- ALIGNED ASSETS - telephone: 01483 306 210 - web: www.aligned-assets.co.uk
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Subject:
However, the results are weird. When you open join.TAB, it maps all the parcels from
table1. The browser
for join.TAB shows the parcel info for the common parcels as well as greyed out
records (similar to a
deleted record) - the same number of grey records as un-joined records in both base
tables. For example,
if both base tables have 10 records, of which 7 are matched, the join.TAB browser will
have 14 lines: 7
with info, 7 greyed.
When you select a parcel in the browser for table2, it does not show a selection on
the map. As well, the
map shows all the parcels from table1. When you select a greyed record, it shows as a
selection in both
the map and the table1 browser. (We use MI 4.1.2)
Very interesting way to spend a Friday afternoon, but not very useful.
Anyone else want to weigh in on this?
Gerald Kornelson
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