> -----Original Message-----
> From: Chris Wagner [mailto:[EMAIL PROTECTED]
> what i want to do is "version" a database. i am not sure if i am
using the right word for > > this, but...
> * where, in the MySQL database could i store a "version number"?
> i know Tables have a "comment" field, which could store a version,
> but the database itself does not have this...
> * how can i bring the database "up-to-date" without losing all rows?
> is there a way to "create a table if it doesn't exist", or
> "remove extra columns and add needed columns if it does exist."
> * OR, is there a better way to do what i want to do, *altogether*???
Yes, there is a 'create table foo if not exist' command, and you can
easily 'alter table' and the other alter commands to add drop and modify
There's no real reason not to store the versioning information in its
own table. Have a 'header' type file to your script always check it and
bounce off a warning telling the user how to run the sql command, so the
admin can run the script (don't want it to just be run-able from anyone
I do a similar thing, although as noone external is deploying my app I
don't have any convenience for it. I have a directory which holds
resources for a given release version. Any added tables and columns go
in there, and then entire table exports also go there (for tables that
hold metadata/etc. about the app) if any of those tables have changed.
The table exports could just be stored as alter statements, but they're
done within the application so it's more trouble than it's worth to try
and track them individually. They also can't be done on the live
version - so I don't have to worry that there are actual values to be
lost in those tables.
So - in summary - header to check, imo version(s) in a separate table,
you could even store the version number each page needs - and just give
a small general warning if the script on the whole doesn't match the
required database version - but still allow using the 'old' parts of the
site. That, however, may be more micromanagement than you want, so
maybe best just to make it an entire 'block' scenario.
The alter statements could, of course, also update the version number as
their last command. All vanilla SQL.
- Martin Norland, Database / Web Developer, International Outreach x3257
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