FreeTDS Development Group

["James K. Lowden" <jklowden AT freetds.org>]

On Tue, 9 Oct 2012 13:33:02 -0400
Evan Panagiotopoulos <epanagio AT gmail.com> wrote:

> During the installation of the package I receive the  prompt:
> 
...
> [ ] MSDBLIB   MS SQL Server support (breaks databases/sybtcl)
> 
> Since I am trying to connect to a MS SQL database I should select the
> last option, MSDBLIB   MS SQL Server support. Is this assumption
> correct? 

Not only is it incorrect, it is groundless.  You should file a bug
report with the packager. 

The --enable-msdblib configuration option causes a lot of confusion.
The confusion, however, is not caused by anything difficult or
complicated about the option.  Rather, it seems to stem from a lack of
knowledge that makes plain language meaningless!  

Many people seem to assume that if their server is made by Microsoft,
then perhaps they need this "MS" option.  

Why *assume*?  Why not just read?  

$ ~/freetds/configure --help | grep msdb 
  --enable-msdblib        for MS style dblib

No mention of SQL Server.  

http://www.freetds.org/userguide/config.htm

        "--enable-msdblib
        Enable Microsoft behavior in the DB-Library API where it
diverges from Sybase's. Use this option if you are replacing
Microsoft's libraries with FreeTDS"

No mention of SQL Server.  

OK, so it's not about the server.  What *is* it about?  

A C program may use the db-lib library, That library was
implemented by Sybase and Microsoft, who defined the names of the
functions and what they do. While the implementations are largely
compatible, there are some small differences.  

For example, dbdatecrack() converts a SQL DATETIME into a DBDATEREC
structure.  The vendors each define that structure in their own way.
For example, Sybase defines a "year" member, but Microsoft defines
"dateyear". Most important, they both define "month", but Sybase says
month is 0-11, and Microsoft says it's 1-12.  

Now, be a C program for a minute.  

        dbsqlexec(dbproc, "SELECT db_date()");
        DBDATETIME *datetime = dbdata(dbproc);
        DBDATEREC daterec;
        dbdatecrack(dbproc, &daterec, datetime);

In daterec.month, you find the value 9.  Does that mean
September or October?  That depends on whose definition of
dbdatecrack() was used.  

FreeTDS is an ecumenical libary.  If you define MSDBLIB either at
configuration time or at compilation time, 9 means September.  If you
don't, it means October.  (There is a runtime aspect, too, that I'm
ignoring for simplicity.) 

What does that mean to the PHP programmer?  PHP is a C program.  You
must know how it will interpret the value or, if it won't interpret the
value, how *you* will.  

If you you have no existing code affected by divergent db-lib
semantics, you can freely ignore --enable-msdblib.  If you do have such
code, you need to enable it or not, as compatibility dictates, else
your date arithmetic could be a month off.  

HTH.  

--jkl