Pitney Bowes MapXtreme - Manual (Page 194)

Chapter 8: Working with Data
Analyzing Data
MapXtreme v7.1 201 Developer Guide
you interact so the SQL tends to be optimal. If you are comfortable with the SQL language using the
ADO.NET method may be more comfortable. But if you are inexperienced with SQL then the OGC
object based query will work just as well.
The MapInfo SQL syntax is defined in the SQL Reference which ships with MapXtreme and is
integrated into Visual Studio after installing MapXtreme. The language is based on SQL3 and has
special MapInfo operators defined for spatial analysis. These operators begin with the MI_ prefix.
MapInfo SQL Language Reference table of contents as displayed in Visual Studio
Data Readers, MemTables and Result Sets
The methods to access data return a data reader or result set. A data reader allows access in a
sequential manner and does not store copies of data. It retrieves the data from the data source,
except in the case where the data source is cached. Result sets are collections of keys. These keys
allow you access back to the original tables and do not create copies of the data.
A MemTable also allows you to store data from various sources into one table. This table type stores
data in a combination of memory arrays and temporary disk storage. When data is added, the
MemTable makes a copy of the data and does not have a key or pointer back to the original table.
These are useful for temporary layers for maps and containers for return values of processes such
as a geocoding or routing result. MemTable access and map rendering performance is equivalent to
native tables.
Result sets are a great tool when you need access to a defined set of rows and when you need to
get data from the source. If the source data may change during your session then this method allows
you to see the results if the data source supports concurrent access. Since MemTables are copies of
data they are a static set of data rows and will not reflect changes from the original data sources.