You can't assign a datatype as otherwise the generated DDL is wrong.
Just to note that the datatype is actually optional in the DDL for a virtual column.
thank you. I didn't look at the exact error message. It says that my VARCHAR2 (xx CHAR) was using a too low number.
It is hard to figure out the correct one here for string-concatenation and -manipulation, so for me it is best to let Oracle figure out the data type. But I get the design rules error in DM then. This is not a deal breaker, but I don't know if it is really an *design error* if you don't specify the datatype for a virtual column. Up to you Just wanted to let you know.
Thanks for the answer,