Firebird 2.1 Language Reference Update

Chapter 10
Changed in: 2.0
Operators and predicates
NULL literals allowed as operands
Description: Before Firebird 2.0, most operators and predicates did not allow NULL literals as operands. Tests
or operations like “A NULL”, “B + NULL” or “NULL < ANY(...)” would be rejected by the parser. Now
they are allowed almost everywhere, but please be aware of the following:
The vast majority of these newly allowed expressions return NULL regardless of the state or value of
the other operand, and are therefore worthless for any practicle purpose whatsoever.
In particular, don't try to determine (non-)nullness of a field or variable by testing with “= NULL” or “ NULL”.
Always use “IS [NOT] NULL”.
Predicates: The IN, ANY/SOME and ALL predicates now also allow NULL literals where they were previously
taboo. Here too, there is no practical benefit to enjoy, but the situation is a little more complicated in that
predicates with NULLs do not always return a NULL result. For details, see the Firebird Null Guide, section
Predicates.
Available in: DSQL, ESQL, PSQL
Text BLOB concatenation
Changed in: 2.1
|| (string concatenator)
Description: Since Firebird 2.1 the concatenation operator supports BLOBs of any length and any character set.
If a mixture of BLOBs and non-BLOBs is involved, the result is a BLOB. If both text and binary BLOBs are
involved, the result is a binary BLOB.
Result type VARCHAR or BLOB
Changed in: 2.0, 2.1
Description: Before Firebird 2.0, the result type of string concatenations used to be CHAR(n). In Firebird 2.0
this was changed to VARCHAR(n). As a result, the maximum length of a concatenation outcome became 32765
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