Beware of Oracle 8i 'nvarchar2' data type

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Impromptu SQL run against fields of this type are 'not supported' by Cognos, which means they will crash the report with a 'dms-e-general' type of error. If you get a strange error on 8i tables, and nothing else appears wrong, examine the table field properties (I use TOAD), and check there are no nvarchars. Export the data out, change the data type, then reload the tables. A related case, from Cognos Knowledge base:

Title: CHAR and VARCHAR data fields in Oracle not retrieved into the catalog.
Product: Impromptu
Version: 6.0
Machine: PC
Document ID: 102586
Replaces:

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Description:

An Impromptu 6.0 catalog was created against Oracle 8.1.6 database. The connection is native. All data fields of a table appear under the database window of the catalog definition screen. However, CHAR and VARCHAR fields do not appear in the catalog folders. These fields are not BLOBs.


Solution:

The data type for character fields was incorrect because the Oracle database was created from a table definition exported from MS SQL Server. All the CHAR and VARCHAR fields had been converted to NCHAR and NVARCHAR fields. These are not standard data types and are not supported by Impromptu. The solution is simply to change the data types back to normal CHAR and VARCHAR fields.