Abstract: A method of processing data stored in a database which comprises a plurality of rows and columns, the method comprising identifying a plurality of sets of column combinations, each set of column combinations comprising an identifier of at least one column allocating each set of column combinations to one of a plurality of nodes mapping the nodes to a lattice structure in which the nodes are connected in a superset or subset relationship according to the set of column combinations of each node selecting a current node processing the data in the set of columns of the current node to detect if the column combination is unique or non-unique traversing the lattice to a next node which is connected to the current node processing the data in the set of columns of the next node to detect if the column combination of the next node is unique or non-unique; and storing a record of whether each processed set of column combinations is unique or non-unique.