Oftentimes we need to do searches that cannot easily be done using any of the previous interfaces, that is when we can use SQL to tailor our search to our needs (SQL = *S*tructured *Q*uery *L*anguage). If we want to find of all proteins with an *R-value < 0.15*, and we want to list their *PDB IDs, deposition date, R-value and resolution*, the SQL statement will look like: To use SQL we need to know the internal structure of the data in the MDB (called the *database schema*), there are no simple and general shortcuts here. Currently the MDB has 22 tables, as shown on the schema generated dynamically: