CREATE TABLE test_lc (x UInt64, lc LowCardinality(Nullable(String))) ENGINE = MergeTree order by x INSERT INTO test_lc SELECT number, number % 10 ? NULL : toString(number % 10000) FROM numbers(10000000) SELECT isNullable(lc) FROM test_lc FORMAT Null SELECT isConstant(lc) FROM test_lc FORMAT Null SELECT isNull(lc) FROM test_lc FORMAT Null SELECT isNotNull(lc) FROM test_lc FORMAT Null