Rob Richardson wrote:
> The database we install at our customers as part of our
> product includes an event_history table. For some reason
> lost in the mists of time, the most important field in that
> table, the description, is a varchar field specified to be
> only 64 characters long. This leads me to a more fundamental
> question: why specify the length of a varchar field at all?
> Is there a big difference between the amount of disk space
> taken up by "abc" stored in a varchar(64) field and stored in
> a varchar field? How much space does an unspecified-length
> varchar field take up? Are there other reasons to use
> varchar(64) instead of varchar?
You can't have "varchar" without a length in parentheses,
as far as I know.
But you can use "text" which is essentially the same thing.
I can think of two reasons to use varchar(n) instead of text:
- you deliberately want to limit the amount of characters.
- you want to index the column (indexes have a maximum row size).
It is not a performance issue, however, and there is no
wasted space either.
Yours,
Laurenz Albe
