If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a simple tool for doing everyday things with PDF documents.
If the MERGE algorithm cannot be used, a temporary table must be used instead. MERGE cannot be used if the view contains any of the following constructs: * Aggregate functions (SUM(), MIN(), MAX(), COUNT(), and so forth) * DISTINCT * GROUP BY * HAVING * LIMIT * UNION or UNION ALL * Subquery in the select list * Refers only to literal values (in this case, there is no underlying table)
Subversion 1.5 will support Merge Tracking. This blog post provides a high level overview of what Merge Tracking is, why it is important and what it means to your organization.
H. chih Yang, A. Dasdan, R. Hsiao, and D. Parker. SIGMOD '07: Proceedings of the 2007 ACM SIGMOD international conference on Management of data, page 1029--1040. New York, NY, USA, ACM, (2007)