The present invention concerns the design and construction of diverse peptide and polypeptide libraries. In particular, the invention concerns methods of analytical database design for creating datasets using multiple relevant parameters as filters, and methods for generating sequence diversity by directed multisyntheses oligonucleotide synthesis. The present methods enable the reduction of large complex annotated databases to simpler datasets of related sequences, based upon relevant single or multiple key parameters that can be individually directly defined. The methods further enable the creation of diverse libraries based on this approach, using multisynthetic collections of discrete and degenerate oligonucleotides to capture the diverse collection of sequences, or portions thereof.