A method of querying a structure of compressed data comprising records stored as a forest of binary includes the step of generating an instruction set allowing a specified data value with a binary tree to be retrieved, given input of an address in memory that identifies the binary tree. Further querying functions which utilise the instruction set allow selection of records on the basis of one or more specified data values, or ranges of data values, statistical analysis of records and grouping of records on the basis of common data values within fields of records.