[freetds] Problem with FreeTDS validating SQL commands

James K. Lowden jklowden at freetds.org
Tue May 20 08:13:16 EDT 2008


Stephane Magne wrote:
> 
> Please correct me if I'm wrong, but it's my understanding that  
> ct_command() ... will also  
> determine if it is valid SQL syntax or if the Stored Procedure call  
> is valid.

I don't think you can depend on that.  I just re-read Sybase's description
of ct_command.  It doesn't imply any interaction with the server, and it
explicitly says the command text need not even by SQL:

 "A language command can be in any language, as long as the server to 
which it is directed can understand it. Adpative Server understands 
Transact-SQL, but an Open Server application constructed with Server- 
Library can be written to understand any language." 

FreeTDS never parses SQL.  If you refer to a nonexistent procedure or
table, you'll hear about it soon enough from the server.  

The ct-lib reference manual gives no reasons for ct_command to return
CS_FAIL, and I don't know of a canonical list of library error messages.  

That's the documentation story.  The implentation and emulation
perspective might be more complicated.  Do you get any more feedback from
Sybase's library besides CS_FAIL?  

> In contrast, the SybaseOpenClient framework will return the CS_FAIL  
> result if the SQL isn't properly formatted.  However, the source  
> isn't readily available to us so we can't compare the two.

I'm not aware the source is available at all, readily or not.  ;-)

What you could do, if you want to investigate further, is use tdsdump(8)
to capture the server interaction, if any, that results from a ct_command
call.  If there's something there, we could take advantage of it.  If
there is none, then I have to say the documented and observed behavior
agree: you can put whatever language text you please into your command
buffer.  It's not an error insofar as the library is concerned.  

HTH.  

--jkl



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