http://www.ianywhere.com/developer/product_manuals/sqlanywhere/0901/fr/html/dbrffr9/00000374.htm
http://orafrance.free.fr/syntaxe_pl_bou.htm
http://sheikyerbouti.developpez.com/pl_sql/?page=Chap4
http://dev.mysql.com/doc/refman/5.0/fr/date-and-time-functions.html