Fine-grained access control for data manipulation language (DML) operations on relational data

Embodiments allow, within database security policies, the grant of data change operation-specific privileges to particular users to be applied within particular data realms in a given table. Furthermore, according to one or more embodiments, User Privilege column-level privileges are explicitly associated with one or more data access operations such that the grant of such a column-level privilege allows the user to perform only those data access operations that are explicitly associated with the column-level privilege. Enforcement of the data security policies includes prevention of data leakage via WHERE and RETURNING INTO clauses. According to one or more embodiments, a two-phase rewrite is used to optimize enforcement of column-level privileges. During the two-phase rewrite of a given query, the privileges checked during enforcement of the User Privilege data security policies are pruned to avoid unnecessary privilege checks given the columns that are accessed in the query.