Methods and systems for generating a database index and searching the database index are described herein. In one aspect this may include receiving an item of database data, wherein the item of database data comprises a sequence of data elements. Groups of data elements may be identified within the received item of database data. If any one or more of the identified groups of data elements have not been previously identified within the item of database data and/or previous items database data then the one or more identified group may be stored as index entries in a database index. Information describing the sequence of the groups of neighbouring data elements may be recorded within the database index as they are located within the item of database data. The database index may be searched based on a received search term comprising a sequence of data elements.