Re: Checking for string data that makes sense Re: postgresql vs mysql

On 22/02/07, Shashank Tripathi <shanx(at)shanx(dot)com> wrote:
> > I would do a CHECK (trim(a) <> '')
>
>
> TRIM() would add some processing time, so I'd include it only if there
> was a chance of spaces getting added. From a puritanical point of
> view, it is definitely a good idea.
>
> To the original poster, this syntax should work in MySQL as well:
>
> create table mytable (mycol text not null check (mycol <> ''));
>
> Problem is, if you created your table before MySQL 5, and now simply
> want to ALTER your table (which is what I gather you wish to do, as
> you already have the table) then adding the CHECK condition may not
> work.
>
> I cannot help in this case, and from the turn this thread has taken,
> not many others I suppose. Why not try a MySQL experts list instead of
> PostgreSQL, but be prepared to have to recreate the table in MySQL 5
> with the CHECK constraint, and then importing your data in to it.
>
> Good luck!
>

Sorry, I spoke too soon. MySQL does not do the constraints jig yet.

"The CHECK clause is parsed but ignored by all storage engines."
- From http://dev.mysql.com/doc/refman/5.0/en/create-table.html

So you may want to adopt some kludges, such as updatable views:
http://arjen-lentz.livejournal.com/49881.html

If I were you, I'd just stick to error-checking in the application
layer for now, or consider slowly switching to PostgreSQL. (No plug
intended)

Shanx