The database system includes: a storage unit that stores a database including an entity data group and a plurality of identifier tables having only a plurality of fixed-length data; and a data processing unit that receives a query and performs data processing on the database on the basis of the received query. Each of the identifier tables includes at least one tuple that is defined in a row direction and at least one attribute field that is defined in a column direction and includes a plurality of data identifiers uniquely indicating the plurality of entity data as the fixed-length data. The database includes a link table that connects the tuples between the identifier tables, in addition to the plurality of identifier tables. The data processing unit performs the data processing using the link table and the identifier tables.