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https://issues.apache.org/jira/browse/DERBY-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13295550#comment-13295550
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Knut Anders Hatlen commented on DERBY-118:
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> a) remove the restriction on VARCHAR defaults length to 254
This one is in accordance with the standard as far as I can tell, and sounds
useful.
> b) remove the restriction that a decimal default cannot lose precision (but
> it can't overflow). It will generate a warning at insert time, though.
>
> The latter doesn't strike me as very useful (probably more likely it would be
> an error, so if you like, I'll omit that one, too).
This sounds very similar to the float -> int type conversion that was rejected
in the previous patch. And, indeed, if someone executes something like this:
create table t1 (x int default 1.1)
or
create table t2 (d decimal(5, 1) default 1234.56)
I'd agree they've most likely mistyped something (either the constant or the
type specifier). So I'm not sure there's much value in accepting them. (I
didn't dive into the details of the standard to see if accepting loss of
precision would also break the store assignment requirements. Wouldn't be
surprised if it did...)
> Lift some DB2 restrictions on DEFAULT values [was: Allow any build-in
> function as default values in table create for columns]
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: DERBY-118
> URL: https://issues.apache.org/jira/browse/DERBY-118
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Bernd Ruehlicke
> Assignee: Dag H. Wanvik
> Priority: Minor
> Attachments: derby-118-all-defaults.diff, derby-118-limited.diff,
> derby-118-limited.status, derby-118-longvarchar.diff, derby-118.diff,
> derby-118.stat, derby-118b.diff, derby-118b.stat, derby-118c.diff,
> derby-118c.stat
>
>
> It is ok in ij to do a values char(current_date) but is is not allowed to
> use char(current_date) as default value for clolumns; like for example
> CREATE TABLE DOSENOTWORK (num int, created_by varchar(40) default user,
> create_date_string varchar(40) default char(current_date))
> Request: It should be allowed to use any build-in function which return a
> valid type as part of the default value spec.
> There was a e-mail thread for this and the core content/answer was:
> Bernd Ruehlicke wrote:
> >
> > CREATE TABLE DOSENOTWORK (num int, created_by varchar(40) default
> > user, create_date_string varchar(40) default char(current_date))
> >
> > give an error as below - any idea why ?!??!
> >
> The rules for what is acceptable as a column default in Derby say that the
> only valid functions are datetime functions.
> The logic that enforces this can be seen in the "defaultTypeIsValid" method
> of the file:
> ./java/engine/org/apache/derby/impl/sql/compile/ColumnDefinitionNode.java
> The Derby Reference Manual also states this same restriction (albeit rather
> briefly):
> ----
> Column Default
> For the definition of a default value, a ConstantExpression is an expression
> that does not refer to any table. It can include constants, date-time special
> registers, current schemas, users, and null.
> ----
> A "date-time special register" here means a date-time function such as
> "date(current_date)" in your first example.
> Since the function "char" is NOT a date-time function, it will throw an error.
> I believe this restriction was put in place as part of the "DB2
> compatibility" work was that done in Cloudscape a while back.
> Hope that answers your question,
> Army
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