SELECT max, then treat the string as a sequence of characters and increment the last character, rippling the carry if there is one :
carry = 1
l = len(s)-1
while carry and l>=0:
c = s[l]
c += carry
if c>max_allowed_char:
c = min_allowed_char
carry = 1
else:
carry = 0
s[l] = cif carry:
s = min_allowed_char + s
If two transactions do the same at the same time, you're out of luck though !
*** Better solution :
if the value was human-entered, prefix it with 'H', if it's auto generated, use 'A' concatenated with the value from a sequence
thus the user-entered values can't clahs with the sequence values ; the sequence values are by definition unique ; and all is well.
or something like that...
On Mon, 3 Jan 2005 11:53:44 -0500, Frank D. Engel, Jr. <[EMAIL PROTECTED]> wrote:
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Is there any "convenient" way to generate (on request) a unique value for a TEXT column? I have a situation in which I want users of my front-end program to be able to manually enter values for this column, but if they leave it blank (in the front-end), to have the database automatically fill in a unique value. I would like to restrict the unique values to (for example) digits and uppercase letters (this is flexible, but the uniqueness of the values should be visually discernible, and all characters should be printable).
I know how to do this with a numeric column (I can just SELECT MAX on the column and add one, for example), but how can this be done with a TEXT column?
Thank you!
- ----------------------------------------------------------- Frank D. Engel, Jr. <[EMAIL PROTECTED]>
$ ln -s /usr/share/kjvbible /usr/manual
$ true | cat /usr/manual | grep "John 3:16"
John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
$ -----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.4 (Darwin)
iD8DBQFB2XiY7aqtWrR9cZoRAqATAJ46xJ3bwsZVpIda0iMSSdcm3/8YKACePSC3 2JAngWmFOlkzC5fNE6HKYMU= =pblY -----END PGP SIGNATURE-----
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---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
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