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 Data Types and SubtypesData Definition (DDL) Statements 

NEXT VALUE FOR

Result type

BIGINT — dialect 2 and 3
INTEGER — dialect 1

Syntax
NEXT VALUE FOR sequence-name

NEXT VALUE FOR returns the next value of a sequence.Sequence is the SQL-standard term for what is historically called a generator in Firebird and its ancestor, InterBase.The NEXT VALUE FOR operator is equivalent to the legacy GEN_ID (…​, increment) function with increment the increment stored in the metadata of the sequence.It is the recommended syntax for retrieving the next sequence value.

Note

Unlike the GEN_ID function, the NEXT VALUE FOR expression does not take any parameters and thus provides no way to retrieve the current value of a sequence, nor to step the next value by a different value than the increment configured for the sequence.GEN_ID (…​, <step value>) is still needed for these tasks.A step value of 0 returns the current sequence value.

The increment of a sequence can be configured with the INCREMENT clause of CREATE SEQUENCE or ALTER SEQUENCE.

In dialect 1, the result type is INTEGER, in dialect 2 and 3 it is BIGINT.
Example
NEW.CUST_ID = NEXT VALUE FOR CUSTSEQ;
See also

SEQUENCE (GENERATOR), GEN_ID()

AT Time Zone Expression

Syntax
<at expr> ::= <expr> AT { TIME ZONE <time zone string> | LOCAL }

The AT expression expresses a datetime value in a different time zone, while keeping the same UTC instant.

AT translates a time/timestamp value to its corresponding value in another time zone.If LOCAL is used, the value is converted to the session time zone.

When expr is a WITHOUT TIME ZONE type, expr is first converted to a WITH TIME ZONE in the session time zone and then transformed to the specified time zone.

Examples
select time '12:00 GMT' at time zone '-03:00' from rdb$database;
select current_timestamp at time zone 'America/Sao_Paulo' from rdb$database;
select timestamp '2018-01-01 12:00 GMT' at local from rdb$database;