1. A computer-implemented method of controlling access to data in a database, comprising: registering a plurality of transformation techniques for a particular column of a table in said database; wherein at least two transformation techniques of said plurality of transformation techniques perform different transformations on actual values of said particular column; after registering the plurality of transformation techniques, receiving a plurality of queries, each query of said plurality of queries being associated with a respective query context and referencing said particular column; computing each query of said plurality of queries, wherein computing each query of said plurality of queries comprises: based on the respective query context of said each query, selecting a transformation technique from the plurality of transformation techniques registered for said particular column; and applying the selected transformation technique to the actual values in said particular column to generate transformed values to use for computing the query in lieu of the actual values in said particular column.