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Posted to derby-dev@db.apache.org by "Bryan Pendleton (JIRA)" <ji...@apache.org> on 2006/11/07 23:56:55 UTC
[jira] Commented: (DERBY-1515) Provide ALTER TABLE functionality to
change a column's data type
[ http://issues.apache.org/jira/browse/DERBY-1515?page=comments#action_12447952 ]
Bryan Pendleton commented on DERBY-1515:
----------------------------------------
Knut Anders pointed out that it isn't necessary to rename column c1 to c1_oldtype.
The technique can be simplified to:
1) ALTER TABLE t ADD COLUMN c1_newtype NEWTYPE;
2) UPDATE t SET c1_newtype = c1;
3) ALTER TABLE t DROP COLUMN c1;
4) ALTER TABLE t RENAME COLUMN c1_newtype to c1;
> Provide ALTER TABLE functionality to change a column's data type
> ----------------------------------------------------------------
>
> Key: DERBY-1515
> URL: http://issues.apache.org/jira/browse/DERBY-1515
> Project: Derby
> Issue Type: New Feature
> Components: Documentation, SQL
> Affects Versions: 10.1.1.0, 10.2.1.6, 10.1.2.1, 10.1.3.1
> Reporter: Bryan Pendleton
> Priority: Minor
>
> Derby should provide a feature which allows a user to change the data type of an existing column in an existing table.
> Currently, there exists the statement:
> ALTER TABLE tablename ALTER COLUMN columnname SET DATA TYPE datatype
> However, this statement currently only allows increasing the length of a VARCHAR column. You are not allowed to decrease the width or to change the data type.
> It would be nice if this restriction could be lifted, and the datatype could be changed.
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