Dear MapInfo SQL Users
I believe that I have discovered a class of MapInfo queries that are
ill-behaved, and whose behaviour has not previously been reported.
These queries have a "calculated column" created by a Select clause
expression involving the ObjectInfo() function.
For example:
Fields {STREET, ObjectInfo(obj,22) "N"}
Tables {Act_st}
Where {}
Group {}
Order {}
Into {Selection}
where Act_st is a StreetInfo file.
(I'm trying to get stats on the numbers of polyline nodes in certain certain
street centreline tables.
ObjectInfo(Obj,22) return the number of nodes in the first section of a
polyline object. For sure my input is a homogeneous polyline table.)
Although the queries execute correctly and create a result set, you cannot:
* use the query result set as input to a Group By query (MapInfo diagnostic
"Unable to create new table")
* save a copy of the query result set (MapInfo diagnostic "Unable to create
new table")
* export the query result set to a MIF file (MapInfo diagnostic "Unknown
error encountered" on import)
The work-around is to permanently add a new column to the base table to hold
the value returned by ObjectInfo() and then use "update table set
N=ObjectInfo(Obj,22) " to store the values.
Can anybody confirm this finding?
David M Haycraft
Information Analysis Associates Pty Ltd
Aust Capital Territory, Australia
Email: [EMAIL PROTECTED]
Web : www.acslink.aone.net.au/actaa/iaa.htm
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