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From "Kristian Waagan (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1645) ALTER TABLE ... SET INCREMENT BY X... Turns off the "Generated By Default" identity column constraint
Date Thu, 19 Oct 2006 10:01:36 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1645?page=comments#action_12443471 ] 
            
Kristian Waagan commented on DERBY-1645:
----------------------------------------

Saurabh, your analysis seem to be identical to what 
I reported in DERBY-1495. I also ran into trouble when trying to fix the problem.
In my case, Derby failed when clearing dependencies for the table when I dropped it.

> ALTER TABLE ... SET INCREMENT BY X... Turns off the "Generated By Default" identity column
constraint
> -----------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-1645
>                 URL: http://issues.apache.org/jira/browse/DERBY-1645
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.1.3.1
>         Environment: Both Ubuntu Linux, Windows XP... Java 1.4.2_x and Java 1.5
>            Reporter: Alan Baldwin
>
> I have a table which has an auto-generated key:
> create table MyTable  (
>    TableId INTEGER GENERATED BY DEFAULT AS IDENTITY NOT NULL,
>    StringValue           VARCHAR(20)           not null,
>    constraint PK_MyTable primary key (TableId)
> )
> I verify that GENERATED BY DEFAULT is set:
> SELECT * FROM 
> sys.syscolumns col 
> INNER JOIN sys.systables tab ON col.referenceId = tab.tableid 
> WHERE tab.tableName = 'MYTABLE' AND ColumnName = 'TABLEID'
> I'm pulling in data for which I need to preserve the ID's:
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (1, 'test1')
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (2, 'test2')
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (3, 'test3')
> In the absense of the Derby 10.2 feature (ALTER TABLE WITH RESTART X), I try to just
change the INCREMENT BY value and insert a row so that I can reset the "next" key value:
> ALTER TABLE MyTable ALTER TableId SET INCREMENT BY 50
> Then I insert a "dummy" record (which I will delete later...) to move the key upwards:
> INSERT INTO MYTABLE (StringValue) VALUES ('test53')
> However, I can now no longer insert explicit values into the primary key like this:
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (-999, 'test3')
> I get this error:  SQL Exception: Attempt to modify an identity column 'TABLEID'. 
> Upon checking the sys.syscolumns table again, it verifies that the table no longer has
an auto-generated key, but the TableId is still an identity column.

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