What package can I use to connect to MS SQL Server through Tcl?
TP TclODBC is not only an option, but a working solution. The other pieces that are required are:
Many main stream Linux distributions already ship unixODBC (RedHat, for one). Compiling unixODBC is fairly easy, just
./configure ; make ; make install
FreeTDS started as a project to provide open source drivers for Sybase. Since MS SQL Server is a re-write of Sybase (MS SQL 7.0 and later; 6.5 and early versions were a direct port of Sybase 4.2), the FreeTDS drivers include protocol specific variances to handle MS SQL Server. The trick is to configure FreeTDS as
./configure --with-tdsver=7.0 ; make ; make install
Use --with-tdsver=8.0 for newest MS SQL Servers.
Compile and install TclODBC.
You'll need to have both a FreeTDS freetds.conf file entry, and an unixODBC odbc.ini file entry to define your MS SQL Server. See the docs for each product.
These are Unix/Linux instructions; if you are already on a Windows box, it should be as simple as just compiling (or installing a pre built-) TclODBC.