Troubleshooting Issues Related To Column Names; Troubleshooting Issues Related To Date Columns - IBM Cognos User Manual

As the modeler, you must ensure that your model columns remain synchronized
with their associated data sources. You can use the Data Sources list to create or
delete columns, and to examine or modify column properties.
For some data sources, Cognos Transformer can automatically identify columns
and assign default column names and properties. However, if your data sources
include IBM Cognos packages or reports, you select specific query objects from an
available list.
Any time that you create columns manually, as you must for fixed-field text files,
you must identify only those data columns that are used in the model. You can
change these assignments later.

Troubleshooting Issues Related to Column Names

When an identically named column appears in two or more data sources, Cognos
Transformer associates each column with a level that has its source column set to
the common name. However, it cannot use matching columns to perform joins on
the source files. Instead, it uses the common name to associate both columns with
categories in the dimension map, or with a measure in the model.
For example, suppose your model has an Order Header data source and an Order
Detail data source. Each contains a column named ORDER_NUMBER. Cognos
Transformer cannot join an Order Header record with an Order Detail record to
create a composite record describing a sales line in an invoice. However, Cognos
Transformer associates the values from both of these sources with a specific level
in one of the dimensions in the model.
To create a join between two columns, use a database query tool such as IBM
Cognos or IBM Cognos Impromptu before you create the data source.

Troubleshooting Issues Related to Date Columns

To obtain the data required to populate the time dimension for your model, you
need at least one data source that includes the required date values. However, in a
model with multiple data sources, date columns may appear in several source files,
and date columns may not relate to your chosen time dimension.
For example, suppose your sales-analysis model contains one source file with order
information, including the order date, and another that contains sales forecasts by
time period. For Cognos Transformer to relate values from both sources to your
chosen time dimension, you must rename the columns that contain the date values
in each source file so that they use the same name.
To ensure that you associate your date values with the appropriate dimension
levels and measures, without increasing the size of the model unnecessarily,
complete the following steps.
Note: If you want to take advantage of Cognos Transformer's relative time
functionality, do not import the date dimensions from dimensional packages.
Instead, use the Insert Data Source option to import the appropriate date field to
create your time dimension.
Procedure
1. Set the absolute range of dates allowed in the model.
2. Match the date format in the model to the format in the source file.
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IBM Cognos Transformer Version 10.1.1: User Guide