Appendix B: Document history

The exact file history is recorded in the manual module in our CVS tree; see http://sourceforge.net/cvs/?group_id=9028

Revision History
0.1	8 Apr 2005	PV	First edition.
0.2	15 Apr 2005	PV	Mentioned that Fb 2.0 legalises “A = NULL” comparisons. Changed text in “Testing if something is `NULL`”. Slightly altered “Dealing with `NULL`s” section.
1.0	24 Jan 2007	PV	This is a major update, with so much new material added that the document has grown to around 4 times its former size. In addition, much of the existing text has been reorganised and thoroughly reworked. It's not feasible to give a summary of all the changes here. Consider this a new guide with 15–25% old material. The most important additions are: `NULL` literals IS [NOT] DISTINCT FROM Internal functions and directives Predicates: IN, ANY, SOME, ALL, EXISTS, SINGULAR Searches (WHERE) Sorts (ORDER BY) GROUP BY and HAVING CASE, WHILE and FOR Keys and indices CHECK constraints SELECT DISTINCT Converting values to `NULL` with `NULLIF` Altering populated tables Bugs list Alphabetical index
1.0.1	26 Jan 2007	PV	Making non-nullable columns nullable again: Provisory fix of error regarding removal of NOT NULL constraints.
1.1	.. Xxx 201x	PV	What is `NULL`?: Added subsection `NULL` as a default state. `NULL` support in Firebird SQL :: Assigning `NULL`: Added 4th example. Predicates :: EXISTS and SINGULAR: “evolves” -> “evaluates” (2x) in Note. Altering populated tables :: Adding a non-nullable field to a populated table :: Adding a NOT NULL field: Added para + additional programlisting after first programlisting. Altering populated tables :: Adding a non-nullable field to a populated table :: Adding a CHECKed column: Added second Note. Altering populated tables :: Adding a non-nullable field to a populated table :: Adding a non-nullable field using domains: Renamed section to Using domains to add a non-nullable field. Altering populated tables :: Adding a non-nullable field to a populated table :: Using domains to add a non-nullable field: Two programlistings instead of one. Text heavily edited and extended. Altering populated tables :: Making existing columns non-nullable :: Making an existing column NOT NULL: Added Warning. Altering populated tables :: Making non-nullable columns nullable again: Largely rewritten, greatly extended and divided into subsections. Changing the nullability of a domain :: New top-level section. For free! Summary: Added “Every field or variable that has been created but not initialised is in a `NULL` state” as second listitem.