Firebird 2.1 Language Reference Update

DDL statements
/* Determines if A is a multiple of B: */
set term #;
create procedure ismultiple (a bigposnum, b bigposnum)
returns (res bool3)
as
declare ratio type of bigposnum; -- ratio is a bigint
declare remainder type of bigposnum; -- so is remainder
begin
if (a is null or b is null) then res = null;
else if (b = 0) then
begin
if (a = 0) then res = 1; else res = 0;
end
else
begin
ratio = a / b; -- integer division!
remainder = a - b*ratio;
if (remainder = 0) then res = 1; else res = 0;
end
end#
set term ;#
Warning
If you change a domain's definition, existing PSQL code using that domain may become invalid. If this happens,
the system table field RDB$VALID_BLR will be set to 0 for any procedure or trigger whose code is no longer
valid. If you have changed a domain, the following query will find the code modules that depend on it and
report the state of RDB$VALID_BLR:
select * from (
select 'Procedure', rdb$procedure_name, rdb$valid_blr from rdb$procedures
union
select 'Trigger', rdb$trigger_name, rdb$valid_blr from rdb$triggers
) (type, name, valid)
where exists
(select * from rdb$dependencies
where rdb$dependent_name = name and rdb$depended_on_name = 'MYDOMAIN')
/* Replace MYDOMAIN with the actual domain name. Use all-caps if the domain
was created case-insensitively. Otherwise, use the exact capitalisation. */
Unfortunately, not all PSQL invalidations will be reflected in the RDB$VALID_BLR field. It is therefore advisable
to look at all the procedures and triggers reported by the above query, even those having a 1 in the
“VALID” column.
Please notice that for PSQL modules inherited from earlier Firebird versions (including a number of system
triggers, even if the database was created under Firebird 2.1 or higher), RDB$VALID_BLR is NULL. This does
not indicate that their BLR is invalid.
The isql commands SHOW PROCEDURES and SHOW TRIGGERS flag modules whose RDB$VALID_BLR field
is zero with an asterisk. SHOW PROCEDURE PROCNAME and SHOW TRIGGER TRIGNAME, which display individual
PSQL modules, do not signal invalid BLR.
COLLATE in variable and parameter declarations
Changed in: 2.1
30