A method, system, method and computer program product for retrieving data. Records are retrieved from a hierarchical database. The records are categorized into a plurality of record types. Each record comprises a unique identifier field. A record map contains zero or more entries. Each entry comprises an identifying value, data from at least one record and a set of Boolean flags. Each flag corresponds to a record type. A computer iterates over the retrieved records. Data from each record is stored at an entry in the record map having an identifying value equal to the value included in the unique identifier field of the record. Moreover, the flag in this entry which corresponds to the record type of the record is set. Inner joins and outer joins are then performed using the contents of the record map.