Allow any build-in function as default values in table create for columns
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Key: DERBY-118
URL: http://issues.apache.org/jira/browse/DERBY-118
Project: Derby
Type: Improvement
Reporter: Bernd Ruehlicke
Priority: Minor
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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