Firebird 2.1 Language Reference Update

DDL statements
• TRANSACTION triggers are executed within the transaction whose opening, committing or rolling-back
evokes them. The actions taken after an uncaught exception depend on the type:
- In a START trigger, the exception is reported to the client and the transaction is rolled back.
- In a COMMIT trigger, the exception is reported, the trigger's actions so far are undone and the commit
is canceled.
- In a ROLLBACK trigger, the exception is not reported and the transaction is rolled back as foreseen.
• It follows from the above that there is no direct way of knowing if a DISCONNECT or TRANSACTION ROLL-
BACK trigger caused an exception.
• It also follows that you can't connect to a database if a CONNECT trigger causes an exception, and that you
can't start a transaction if a TRANSACTION START trigger does so. Both phenomena effectively lock you
out of your database while you need to get in there to fix the problem. See the note below for a way around
this Catch-22 situation.
• In the case of a two-phase commit, TRANSACTION COMMIT triggers fire in the prepare, not the commit
phase.
Note
Some Firebird command-line tools have been supplied with new switches to suppress the automatic firing of
database triggers:
gbak -nodbtriggers
isql -nodbtriggers
nbackup -T
These switches can only be used by the database owner and SYSDBA.
Domains instead of datatypes
Changed in: 2.1
Description: Firebird 2.1 and up allow the use of domains instead of SQL datatypes when declaring local trigger
variables. See PSQL::DECLARE for the exact syntax and details.
COLLATE in variable declarations
Changed in: 2.1
Description: Firebird 2.1 and up allow COLLATE clauses in local variable declarations. See PSQL::DECLARE
for syntax and details.
NOT NULL in variable declarations
Changed in: 2.1
Description: Firebird 2.1 and up allow NOT NULL constraints in local variable declarations. See
PSQL::DECLARE for syntax and details.
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