A Datatype in Excel is a “might be” Datatype
Let’s have an example with a Date, a Number and a Currency. Well formatted…

But in fact we are allowed to input whatever we want…

Even the format has not been changed.

In the DWH Builder it looks like this
All columns are Character Fields because the first 20 rows are taken to check for the format is and how the corresponding values are.
The format here is different to the content of the columns so that Character will be taken. And the Row with the “wrong” values will be shown.

Let us change the Excel File and do the first 20 Rows correctly

How about the DWH Builder?
Now the DWH Builder recognizes that these Columns are datetime and float. (Dataytpe Currency will be converted to float in the DWH Builder)
And the Row with the wrong values will be omitted.
