Firebird Null Guide

NULL behaviour and pitfalls in Firebird SQL, Paul Vinkenoog, 26 January 2007 – Document version 1.0.1

• What is NULL?
• NULL support in Firebird SQL
• NULL in operations
• Internal functions and directives
• Predicates
• Searches
• Sorts
• Aggregate functions
• Conditional statements and loops
• Keys and unique indices
• CHECK constraints
• SELECT DISTINCT
• User-Defined Functions (UDFs)
• Converting to and from NULL
• Altering populated tables
• Testing for NULL and equality in practice
• Summary
• A: NULL-related bugs in Firebird
• B: Document history
• C: License notice