How to define a driver for tclodbc?

问题

I want to use tclodbc from Linux environment to connect to a MS SQL server. I have the driver (freeTDS) and the connection string. But I don't know how to configure the driver to be used by tclodbs. There is a command

database configure operation driver attributes

But I don't know what to put as operation and attributes, and whether this is the right command.

Related to my question: Accessing Microsoft SQL Server from Tcl running on GNU/Linux

回答1:

OK, here's my take based on these guides about how to make a DSN-less connection using the FreeTDS driver.

I've tested it a Debian Lenny system having tclodbc 2.5-5, unixodbc 2.2.11 and libdbd-freetds 0.8.2-1-4.1 and tcl 8.4.16-2 installed against an instance of Microsoft SQL Server 2005.

package require tclodbc

proc cs_append {varName args} {
    set alen [llength $args]
    if {$alen < 2 || $alen % 2 != 0} {
        return -code error "Wrong # args: should be varName key value ?key value?"
    }

    upvar 1 $varName qs

    foreach {key value} $args {
        if {$qs ne ""} {
            append qs \;
        }
        append qs $key = \{ [string map {\{ \\\{} $value] \}
    }
}

set user test
set pass secret

set cs ""
cs_append cs DRIVER FreeTDS UID $user PWD $pass \
    Server myserver.domain.local \
    ClientCharset UTF-8 \
    APP "My test app"

database connect db $cs
foreach row [db {select * from MyDatabase..MyTable}] {
    puts $row
}
db disconnect

Some notes:

The FreeTDS driver must be known to the ODBC subsystem by means of it being registeded in the /etc/odbcinst.ini file. I suppose that at least on my system appropriate packages take care of this by themselves but you'd better verify if you have FreeTDS registered in that file, otherwise that DRIVER=FreeTDS bit in the connection string won't work as ODBC will have no idea how to load the named driver library.
The ClientCharset and APP connection string parameters do not work in my case. While I can live with the second, the first one sucks big time because in this case the character data is returned in some botched encoding.

But there's no such problem when I use named server from the /etc/freetds/freetds.conf file using the ServerName=THAT_SERVER instead of Server=SERVER_HOST in the connection string. Unfortunately, this kind of defeats half of the purpose of using DSN-less setup.

Quite possibly it's a bug in my version of the FreeTDS driver, and I have a really outdated system here, so YMMV and you better check yourself on your system.

回答2:

If we look at the documentation, we see that there are 6 operations, of which the one you probably want is add_dsn. An example is included (below, with a small correction):

set driver "Microsoft Access Driver (*.mdb)" 
set attributes [list "DSN=mydsn" "DBQ=c:\mydb.mdb" "FIL=MS Access"] 
database configure add_dsn $driver $attributes

I'm afraid you'll have to consult the FreeTDS documentation to get the right collection of attributes, but I think (based on this evidence) that you'll have the driver being FreeTDS and the attributes might be OK if it is an empty list (or with just TDS_Version=5.0 in it). I really don't know too much about configuring ODBC…

来源：https://stackoverflow.com/questions/10829621/how-to-define-a-driver-for-tclodbc

标签

sql

odbc

tcl

freetds