Is there a field length I should not exceed for my primary key field length if I want to be compatible with most DBMS?

what is the datatype of this key that you have in mind?

when people speak of "field length" it usually means a VARCHAR column, but i thought i'd ask to make sure

I'm drawing the ERD in visio, which uses Access perspective. Char. type is TEXT, though VARCHAR would work as well. Does the answer differ between the two?

What's the maximum length? And the RDBMS?

pootle flump ur codings are working excelent.

Since I'm building a generic model (I don't know what RDBMS I'll employ, though I'm using Access for now), I'm looking for a rule-of-thumb figure. I'm trying to avoid having to change field names later, depending upon what RDBMS I settle on.

rule of thumb: maximum 255 bytes

any more than that and i would question the viability of this column as a key

and you would ~never~ need to adjust a column name based on the RDBMS chosen, assuming you do not use special characters in the name


say, i just realized something -- are you talking about the length of the column, or the length of the name of the column???

Originally, I was interested in the column length. I could imagine using a primary key with say 10 ANSI characters, so c. 20 bytes. (2 bytes per char. with ANSI chars, right?).

However, what is the max length of a field/column name?

I see now how I confused things inserting "field names." I did mean field lengths. I was thinking about two things as I was writing. Sorry 'bout that.

2 bytes per character only in some character encodings (unicode?)

maximum length of column for viability as a key is (in my opinion) 255 bytes, preferably substantially less

maximum length of column name varies by database system (access 64, sql server 128, as little as 6 characters for a couple of older ones) but for practical purposes shouldn't be any longer than ~40 characters