copying a column

[usaims]

I'm learning how to copy columns and I'm having a little trouble.
The column that I'm trying to copy is from the same database. Correct
me if I am wrong, but I think you have to create the column in the
database first? Here is the command that I'm using, but its not
working, obviously.

mysql> alter table bugs add column test mediumint(9) NOT NULL
auto_increment;
ERROR 1075 (42000): Incorrect table definition; there can be only one
auto column and it must be defined as a key

Here is the table that has the column that I'm trying to copy from:

mysql> describe bugs \G
*************** ************ 1. row *************** ************
Field: bug_id
Type: mediumint(9)
Null:
Key: PRI
Default: NULL
Extra: auto_increment

Can somebody give me a clue. Also, I'm looking for detailed
documentation on primary keys, if somebody has such a link, please send
it to me, thanks in advance.

usaims

[Felix Geerinckx]

Re: copying a column

On 14/06/2005, usaims wrote:
[color=blue]
> I'm learning how to copy columns and I'm having a little trouble.
> The column that I'm trying to copy is from the same database. Correct
> me if I am wrong, but I think you have to create the column in the
> database first?[/color]

You don't create columns in a database, but in a table (which lives in
a database)
[color=blue]
> Here is the command that I'm using, but its not
> working, obviously.
>
> mysql> alter table bugs add column test mediumint(9) NOT NULL
> auto_increment;
> ERROR 1075 (42000): Incorrect table definition; there can be only one
> auto column and it must be defined as a key
>
> Here is the table that has the column that I'm trying to copy from:
>
> mysql> describe bugs \G
> *************** ************ 1. row *************** ************
> Field: bug_id
> Type: mediumint(9)
> Null:
> Key: PRI
> Default: NULL
> Extra: auto_increment
>
> Can somebody give me a clue.[/color]

You already have an auto_increment column in your table and you only
can have one: so you cannot add another
[color=blue]
> Also, I'm looking for detailed
> documentation on primary keys, if somebody has such a link, please
> send it to me, thanks in advance.[/color]

Type 'primary key' in a google search box.

--
felix