My situation is the following: suppose you have something like:

CREATE TABLE t1(
  mykey VARCHAR(255) primary key,
  myvalue VARCHAR(255)
);

Since Sybase is case-sensitive over the column values, something like this would be allowed:

INSERT INTO t1(mykey, myvalue) VALUES('key', 'value');
INSERT INTO t1(mykey, myvalue) VALUES('KEY', 'VALUE');

Result:

+-----+-------+
| key | value |
+-----+-------+
| KEY | VALUE |
+-----+-------+

I actually want to prevent this, and the second insertion should fail for duplicated key. Anyway, if I want to modify the value of any other column which is not primary key, for example from 'value' to 'VaLuE', I want to be able to do that, preserving the case insensitivity constraint only on the primary key.

This is possible on Oracle by creating an upper/lower case index on the table:

CREATE INDEX myindex ON t1(UPPER(mykey));

Anyway this doesn't seem to work on Sybase, since the duplicated-case insertion is still allowed.

I've found some hints around the web which would act on the DBMS configuration, through sp_configure/sp_text_configure, but I want to avoid such an intrusive solution, and apply the case sensitivity ONLY to some specific tables and ONLY on the primary keys of those tables, like I do on Oracle by creating the index through the syntax shown above.

Is this possible on Sybase?