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https://issues.apache.org/jira/browse/DERBY-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13282025#comment-13282025
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Dag H. Wanvik commented on DERBY-118:
-------------------------------------
Looking at the standard, I see that the default value is defined as
<default option> ::=
<literal>
| <datetime value function>
| USER
| CURRENT_USER
| CURRENT_ROLE
| SESSION_USER
| SYSTEM_USER
| CURRENT_PATH
| <implicitly typed value specification>
This would seem to preclude a cast in the form of CHAR(CURRENT_DATE),
but this would be ok:
CREATE TABLE ok (create_date_string VARCHAR(40) DEFAULT CURRENT_DATE)
and similarly for CURRENT_TIME and CURRENT_TIMESTAMP. We do allow this
implicit coercion on INSERT. Uploading a proof-of-concept patch which
makes the above table creation work: derby-118.diff. No tests yet,
running regressions.
> 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
> Priority: Minor
> Attachments: derby-118.diff, derby-118.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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