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From "Kathey Marsden (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-275) Add documentation support for BY DEFAULT option, once code changes are made.
Date Fri, 24 Jun 2005 17:05:04 GMT
    [ http://issues.apache.org/jira/browse/DERBY-275?page=comments#action_12314405 ] 

Kathey Marsden commented on DERBY-275:
--------------------------------------

REGARDING THIS PARAGRAPH:

Note that unlike a GENERATED ALWAYS column, a GENERATED BY DEFAULT column does not guarantee
uniqueness. Thus, in the above example, the hi and salut rows will both have an identity value
of "1", because the generated column starts at "1" and the user-specified value was also "1".
To prevent this, you can use the "STARTS WITH" keyword described below. To check for this
condition and disallow it, you can use a primary key or unique constraint on the GENERATED
BY DEFAULT identity column.

In the paragraph STARTS WITH should be START WITH and loading or importing data should be
covered.

CHANGE:
To prevent this, you can use the "STARTS WITH" keyword described below. 

TO:

To prevent  duplication especially when loading or importing data, create the table using
 a "START WITH" value which corresponds to the first 
identity value that the system should assign.

ADD AN EXAMPLE:

create table greetings
        (i int generated by default as identity (START WITH 2, INCREMENT BY 1),
 ch char(50));
-- specify value "1":
insert into greetings values (1, 'hi');
-- use generated default
insert into greetings values (DEFAULT, 'salut');
-- use generated default
insert into greetings(ch) values ('bonjour');



> Add documentation support for BY DEFAULT option, once code changes are made.
> ----------------------------------------------------------------------------
>
>          Key: DERBY-275
>          URL: http://issues.apache.org/jira/browse/DERBY-275
>      Project: Derby
>         Type: Sub-task
>   Components: Documentation
>     Versions: 10.0.2.1
>     Reporter: Satheesh Bandaram
>      Fix For: 10.1.1.0
>  Attachments: derby275finaldraftmodified.zip
>
> Once a patch is accepted, new syntax needs to be documented.

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