[jira] [Commented] (DERBY-118) Allow any build-in function as default values in table create for columns

["Knut Anders Hatlen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287356#comment-13287356 ] 

Knut Anders Hatlen commented on DERBY-118:
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Syntax rule 4b says that the length of the character column must be at least 128 if the default is CURRENT_USER, so the standard is in fact even more restrictive than Derby in that case. The standard doesn't seem to allow CURRENT_SCHEMA in the default clause (I don't think CURRENT_SCHEMA is mentioned in the standard at all), but it seems like the 128 character restriction is in the spirit of syntax rule 4b, so it sounds reasonable to keep it.
                
> 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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