The categories list for each user is held in their Windows registry. Each
version of Outlook has a slightly different path to the categories list and
Outlook 2000 and earlier use a string registry value and Outlook 2002 and
later use a binary value that uses Unicode to store the categories.

So your SQL categories would have to be copied to the correct registry
location for each user depending on their Outlook version and the strings
would have to be converted into Unicode if the user was running Outlook 2002
or later. Or if the SQL data is already Unicode you'd have to convert into
ANSI strings for versions earlier than Outlook 2002.

See http://www.slipstick.com/outlook/olcat.htm for information on the
registry paths.