One column as system.columns reports it.
system.columns
Whether the column holds several values per record: an empty array is a record without any.
The type without LowCardinality(...) and Nullable(...).
LowCardinality(...)
Nullable(...)
Whether the column is Nullable(T): the only columns that can tell a missing value from a default.
Nullable(T)
The type an operand of this column is bound as: its base type, except where the text form differs.
Whether the column stores instants natively; its operands and positions travel as epoch milliseconds.