New Null Guide beta

There’s a new Null Guide beta at
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide.html
The following things have been added since the previous beta:

New section “Predicates”, with IN, ANY, SOME, ALL, EXISTS, SINGULAR
(IN was already present but has undergone some changes)
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-predicates.html

– Added to section “Aggregate functions”:
Counting frequencies
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-aggrfunc.html#d0e14798
The HAVING clause
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-aggrfunc.html#d0e14854

– New section “Conditional statements and loops”, with IF, CASE, WHILE, FOR
(IF was already present in the guide)
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-conditionals-loops.html

– In section “Altering populated tables”, an explanation has been
added as to *why* NULLs are sometimes falsely reported as zeroes.
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-alter-pop-tables.html#d0e16766

– Quite a few items have been added to the Summary.
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-summary.html

– Bugs list: some bugs added, and some more links to and from the bugs list
added – but only where the linked-to spot contains extra information.
http://www.firebirdsql.org/devel/doc/manual/temp/nullguide/nullguide-bugs.html

I intend to put the new guide up in a couple of days. In the meantime,
please let me know if you notice any errors (except widows/orphans and
other page-break related stuff).

Greetings,
Paul Vinkenoog