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From "Bryan Pendleton (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (DERBY-119) Add ALTER TABLE option to change column from NULL to NOT NULL
Date Wed, 16 Aug 2006 06:15:16 GMT
     [ http://issues.apache.org/jira/browse/DERBY-119?page=all ]

Bryan Pendleton updated DERBY-119:
----------------------------------

    Attachment: alterColumnNotNull_v3.diff

Hi Deepa, thanks for re-reviewing the patch. I think your idea about renaming the 
SQLState constant is a good one. Attached is alterColumnNotNull_v3.diff, which
 differs from alterColumnNotNull_v2.diff in that it renames 
      LANG_MODIFY_COLUMN_PKEY_CONSTRAINT
to
     LANG_MODIFY_COLUMN_EXISTING_CONSTRAINT


> Add ALTER TABLE option to change column from NULL to NOT NULL
> -------------------------------------------------------------
>
>                 Key: DERBY-119
>                 URL: http://issues.apache.org/jira/browse/DERBY-119
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>            Reporter: Bernd Ruehlicke
>         Assigned To: Bryan Pendleton
>         Attachments: alterColumnNotNull_1.diff, alterColumnNotNull_v2.diff, alterColumnNotNull_v3.diff
>
>
> There was a thread about this on the Cloudscape forum
> http://www-106.ibm.com/developerworks/forums/dw_thread.jsp?message=4103269&cat=19&thread=59941&forum=370#4103269
> Since this describes the problem I will just copy the content of this entry as my dexscription
> The content of this was 
> "
> Hi,
> I stumbled across a behaviour of cloudscape which is not a bug but IMHO an implementation
choice. To assign a primary key to a table using ALTER TABLE all columns must be declared
NOT NULL first, which can only be specified upon column creation (no ALTER TABLE statement
exists to change the NOT NULL property of a column).
> Most databases I know do two things differently:
> 1) when a primary key is assigned all pk columns are automatically set to NOT NULL, if
one of them contains NULL values, the ALTER TABLE statement fails
> 2) it is possible to alter the column to set the NOT NULL property after column creation
(fails when there are already records containing NULL values)
> If I have understood the limitations correctly in Cloudscape I have no choice but to
remove and re-add the column which is supposed to be used in the primary key, if it is not
already declared as NOT NULL. This means that in the case of a table containing valid data
(unique and not null) in the column in all records, I would have to export the data, remove
and re-add the column and reimport that data, which would not be necessary e.g. in Oracle
or MaxDB.
> Is it possible to change that behaviour or is there a good reason for it? It looks as
if it makes the life of the user more difficult than necessary for certain metadata manipulations.
Making it possible to alter the NOT NULL property of a column would solve this and IMHO having
a primary key constraint do this implicitly makes sense as well. 
> Thanks in advance for any insight on this,
> Robert"

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