Actually we don't have the full DNA sequence for any human. For example, if you look at the data from say the Genome Reference Consortium the first 10,000 bases on Chromosome are designated as N - unknown.
There are a bunch of regions of 'N' in the reference sequence, most are just repeats.
The genome is incredibly complex, and yes, much we still can't represent accurately. As one example, some genes are given a location in the reference genome, while every person actually has multiple copies that are scattered across the genome.