Reported for version 8
Fields with white spaces in DB tables are considered NULL in the Column Analysis statistics, usually, for a DB a blank space is not the same as NULL.
Or, the minimum and maximum lengths found were 1 character and there are no zero-length (null or empty string) occurrences. If a field is not nullable and of fixed width, then spaces are a valid non-null value.
This is the intended behavior of DQC. In fields containing empty strings and trailing whitespace: the whitespace is removed and if the result is an empty string, it is treated as NULL.The rationale behind this is from the data quality point of view. A blank field and a NULL bear the same information - that the field is not filled in.
The minimum length is calculated from the non-null values only - so the minimum will be always greater than zero.