and including 1.5. This bug was fixed in v.1.5.1. From that version onward, such a statement will yield an empty result set. 3.2. Boolean operations All the operators examined so far return NULL if any exactly 1 row; • false if the search condition is true for more than 1 row. Whether the other rows yield false, NULL or a combination thereof, is irrelevant. NOT SINGULAR will always return the opposite integer type, AVG is always rounded towards 0. For instance, 6 non-null INT records with a sum of -11 yield an average of -1, not -2. [2] LIST was added in Firebird 2.1 Chapter 8. Aggregate functions 28