The Microsoft ODBC Driver 17 for SQL Server has been available for Linux for a while now, but I recently had a bit of trouble getting it to work with SQL Relay on CentOS 6.9. Just in case anyone else has had similar trouble, here's what I ran into, and here's how I fixed it.
The CentOS/RHEL 6 RPM's are available at https://packages.microsoft.com/rhel/6.8/prod/.
The driver itself is msodbcsql17-17.1.0.1-1.x86_64.rpm but if you try to install it using yum localinstall or rpm -i then it will complain that it needs a newer version of unixODBC than what is available for CentOS/RHEL 6. Version 2.3.1, in particular.
Fortunately, there are some unixODBC-2.3.1 rpms available in the same directory. Sort of...
Actually, there's a unixODBC-devel-2.3.1 rpm and some odd unixODBC-utf16 rpms, but the requested unixODBC-2.3.1 rpm is missing.
It turns out that a unixODBC-2.3.1 package was there at one point, but has since been removed. It's kind-of good that it was removed because it didn't always work. It worked with isql, but any calls to SQLConnect() by SQL Relay (and presumably by other apps) would reliably hang. What can we do though? The msodbcsql17 rpm requires unixODBC-2.3.1.
Well, those utf16 packages actually do work with msodbcsql17, and don't cause SQLConnect() to hang, but getting everything to install requires a little finesse.
I was able to get everything to install by running:
yum remove unixODBC unixODBC-devel yum localinstall unixODBC-utf16-* rpm -i --nodeps msodbcsql17-17.1.0.1-1.x86_64.rpm
The --nodeps option is important because it enables the rpm to install without checking dependencies.
After that I reconfigured, rebuild, and reinstalled SQL Relay and everything worked for me.
