[jira] Resolved: (DERBY-1926) Provide documentation for ALTER TABLE DROP COLUMN

["Bryan Pendleton (JIRA)" <de...@db.apache.org>]

     [ http://issues.apache.org/jira/browse/DERBY-1926?page=all ]

Bryan Pendleton resolved DERBY-1926.
------------------------------------

    Fix Version/s: 10.3.0.0
       Resolution: Fixed
       Derby Info:   (was: [Patch Available])

Comitted the doc patch to the docs trunk as subversion revision 462850.

Once the updated doc appears on the web site I'll close this issue.


> Provide documentation for ALTER TABLE DROP COLUMN
> -------------------------------------------------
>
>                 Key: DERBY-1926
>                 URL: http://issues.apache.org/jira/browse/DERBY-1926
>             Project: Derby
>          Issue Type: New Feature
>          Components: Documentation
>    Affects Versions: 10.3.0.0
>            Reporter: Bryan Pendleton
>         Assigned To: Bryan Pendleton
>            Priority: Minor
>             Fix For: 10.3.0.0
>
>         Attachments: dropCol1.diff
>
>
> The documentation will need to be updated after DERBY-1489 is committed. The reference manual will need to describe how to use the new ALTER TABLE DROP COLUMN feature to drop a column from a table.
> The documentation for the ALTER TABLE command is becoming somewhat unwieldy, so perhaps there is a way to restructure the page to make it easier and more approachable.
> In the documentation, it will be important to clearly describe the RESTRICT and CASCADE behaviors, as users may be confused by what things cause RESTRICT to refuse to drop a column. The comments in AlterTableConstantAction.java may help.
> Specifically, the documentation should note these possibly unexpected behaviors:
>  - If a column is present in one or more indexes, these indexes by themselves do not cause
>    RESTRICT to refuse to drop a column. Instead, the column will simply be dropped from
>    the index, and if that was the last column in that index, the entire index will be dropped.
>  - Explicitly named CHECK constraints will cause RESTRICT to refuse to drop a column, as
>    will PRIMARY KEY, FOREIGN KEY, and UNIQUE constrants. However, an unnamed simple
>    NOT NULL constraint on a column will NOT cause RESTRICT to refuse to drop it.

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