Some companies use Hand-Written Electronic-Schemes or typed electronic-schemes but without the original digital format. Some times, it would be useful to have the digitalized format of these schemes to update some of their parts or design new ones through CAD programs. In this paper, we do not explain the whole electronic-scheme analysis application but we deep on the database module. This module is crucial if we want a high recognition ratio in a reasonable run-time. We represent the electronic components by graphs and we evaluate, on one hand, different structures useful to encode a set of graphs, and on the other hand, indexing structures for fast querying of these graphs.