Is there an ANSI standard for auto-numbered columns.
Currently, we have a choice of SERIAL, AUTOINCREMENT, AUTO_INCREMENT, IDENTITY() and good old NEXTVAL() among others.
I read somewhere that there is a new standard using IDENTITY which I know that Oracle has recently implemented. I know that Oracle is hardly the last word on standards.
If there is a standard, then it’s a long time coming.
Yes there is, and it's definitely not "a new standard". It's been in the SQL standard since SQL:2003
The definition is:
<identity column specification> ::=
GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY
[ <left paren> <common sequence generator options> <right paren> ]
The optional part with the sequence generator options lets you define the characteristics of the underlying sequence (=generator), you could do something like:
id integer GENERATED ALWAYS AS IDENTITY (start with 42 increment by 10 cycle)
This syntax is supported (at least) by PostgreSQL 10, Oracle 12.1, DB2, Apache Derby, HSQLDB, Firebird and NuoDB.
SQL:2003 was just what I needed to find more information. I found this link: sigmodrecord.org/publications/sigmodRecord/0403/…. I don’t think it’s widely supported, is it?
– Manngo
Feb 20 '17 at 6:48
