[
http://issues.apache.org/jira/browse/DERBY-382?page=comments#action_12314720 ]
Jeff Levitt commented on DERBY-382:
-----------------------------------
Adding Kathey Marsden's comment on Derby-275 that was added after that issue
was committed:
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');
> Doc Review (CLOSED TO FURTHER COMMENTS): Derby Reference Manual
> ---------------------------------------------------------------
>
> Key: DERBY-382
> URL: http://issues.apache.org/jira/browse/DERBY-382
> Project: Derby
> Type: Improvement
> Components: Documentation
> Environment: all
> Reporter: Jeff Levitt
> Priority: Minor
> Fix For: 10.1.1.0
>
> This issue tracks comments for the Derby Reference Manual. The deadline for
> posting comments was Tuesday, June 28, noon Pacific time.
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