I see you are having difficulty with this concept. . . If you have 100 bytes of data (the actual number does not matter) and try to put this into a 30-byte column - it will not go in there.
What is the idea way to show it full and in 1 row.
If it will not fit, there is no "idea way". You can truncate the data before the load or you can just let it be lost. If you actively look at the data and report length problems, it may help resolve the problem.
Unless i've missed something i see 3 alternatives:
Change the table definition to prevent truncation.
Change the data to fit.
Just do nothing and live with it.