FreeTDS Development Group

[Igor Korot <ikorot01 AT gmail.com>]

James,

On Wed, Oct 10, 2012 at 8:41 PM, James K. Lowden <jklowden AT freetds.org> wrote:
> 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.

As you said yourself, there are differences between Sybase and
Microsoft in their
implementation. You just described one of them.

Is there a list of such differences available and where it is located?
If not, maybe it is
worth making it and refer to it in the UG?

Thank you.

>
> HTH.
>
> --jkl
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