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https://issues.apache.org/jira/browse/DERBY-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13286958#comment-13286958
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Dag H. Wanvik commented on DERBY-118:
-------------------------------------
Note: I did not go as far as to allow expressions, so Derby is still limited
relative to Cloudscape here, we stick to literals as prescribed by the
standard, although we allow more implicit conversions than the standard.
> 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-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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