The during load transformation allows the manipulation of column data as it enters the data warehouse.
By default, Database link loads and ODBC based loads have During and After transformations enabled. 
When transformations are enabled, the contents of a source table/source column for each column are used as the basis of the loading statement.
- If the source table and source column are null, then a null is used.
- If data exists in the Transformation tab of a column's properties, then this transformation data is used instead of the source table/source column combination.
Example
The following load table columns will generate the load sql statement if no transformation data is present against these columns.
The SQL code from the load results is:
If the Column has a transformation defined as follows:
UPPER(substring(description,1,1)) + LOWER(substring(description,2,1))
then the following SQL statement will be executed.