Good point. In the described case the OR terms were guaranteed to be disjoint, in a way the query planner could easily figure out. Which Sybase's planner did.

Good point. In the described case the OR terms were guaranteed to be disjoint, in a way the query planner could easily figure out. Which Sybase's planner did. However for cases like described in the article, you'd need to handle that. While I like CTEs, I've had more consistent luck with subqueries. They also compose more easily.