Systems, methods, and storage mediums for retrieving data are provided. A syntax analysis is performed of a retrieval request according to data definition information in a data dictionary so as to convert the retrieval request into a query statement executable by a database. The database comprises an unnormalized data structure that violates the first, second, or third normal condition. The data definition information is for converting the unnormalized data structure to a logically normalized data structure. The data dictionary comprises display tables and logical items. A display table comprises a plurality of display items. Each display item corresponds to a logical item. The query statement is executed relative to the database so as to obtain a retrieval result. The obtained retrieval result is edited according to the data definition information so as to generate a final retrieval result.