Cursor expression queries that include the UNION clause between SQL statements selecting columns that are protected by Oracle Data Redaction policies may return fewer rows.

This happens because redaction is performed on the column first and then the UNION clause is applied on the redacted data from the SELECT statements.

To work around this issue, rewrite the queries to include an inline view so that the UNION operation occurs before redaction. For example, instead of the following queries:

SELECT cursor(SELECT sensitive_column FROM table_name
              UNION
              SELECT sensitive_column FROM table_name);

Rewrite the queries as follows:

SELECT cursor(SELECT sensitive_column FROM
    (SELECT sensitive_column FROM table_name
    UNION
    SELECT sensitive_column FROM table_name));