When running AbstractFunctionalWorkflowTest test case using Oracle database, the following code :

// --------------------------- empty nested query : AND
// ---------------------------------
Expression queryLeft = new FieldExpression(FieldExpression.OWNER, FieldExpression.CURRENT_STEPS, FieldExpression.EQUALS, USER_TEST);
Expression queryRight = new FieldExpression(FieldExpression.STATUS, FieldExpression.CURRENT_STEPS, FieldExpression.EQUALS, "Finished");
query = new WorkflowExpressionQuery(new NestedExpression(new Expression[] {queryLeft, queryRight}, NestedExpression.AND));
workflows = workflow.query(query);

fails with the exception:
com.opensymphony.workflow.StoreException: SQL Exception in query: ORA-00933: SQL command not properly ended
at com.opensymphony.workflow.spi.jdbc.JDBCWorkflowStore.doExpressionQuery(JDBCWorkflowStore.java:1197)
at com.opensymphony.workflow.spi.jdbc.JDBCWorkflowStore.query(JDBCWorkflowStore.java:621)

the query used is:
SELECT DISTINCT (a1.ENTRY_ID) AS retrieved FROM OS_CURRENTSTEP AS a1 , OS_CURRENTSTEP AS a2
WHERE a1.ENTRY_ID = a1.ENTRY_ID AND a1.ENTRY_ID = a2.ENTRY_ID AND ( a1.OWNER = 'test' AND a2.STATUS = 'Finished' )

This is because AS token is not supported in table reference (FROM) by Oracle.