Hi all
We plan to write large application (sales, purchase, accounting) in C/C++.
It will work with DB2 and other databases (MS SQL and Oracle). Client will
work under Win and Linux, so ADO and OLE DB aren't solution.
It seems ESQL standard is the only solution that allows to write such
application once and connect to different databases. Is this good choice? Is
this fit for serious application? Will it be supported in the future?
In your opinion, which API would be the best solution?

your help would be greatly appreciated
Tomasz

Depends upon whether your SQL is static or not. And ... I don't believe MS or
Oracle support embedded SQL. You may want to take a more dynamic approach and
look at the CLI interface.

Larry Edelstein

Tomasz wrote:

DB2 Federated Database Technology provides the mechanism of
integrating multiple data sources.
http://www-900.ibm.com/developerWork...haas_eng.shtml

"Tomasz" <rn55 (AT) nospam (DOT) wp.pl> wrote

While stranded on information super highway Tomasz wrote:
Hi all
We plan to write large application (sales, purchase, accounting) in C/C++.
It will work with DB2 and other databases (MS SQL and Oracle). Client will
work under Win and Linux, so ADO and OLE DB aren't solution.
It seems ESQL standard is the only solution that allows to write such
application once and connect to different databases. Is this good choice? Is
this fit for serious application? Will it be supported in the future?
In your opinion, which API would be the best solution?

your help would be greatly appreciated
Tomasz


I am in process of porting our application from DB2 to Oracle. We
use embedded SQL and it is relatively easy to port from one database to
another as long as you do not use LOBs, and make sure that the date/time
settings are same across the database so you can specify date/time in one
format (e.g. YYYY-MM-DD). We use LOBs and VARCHARS which require some
tweaking of the code. If you use "FOR FETCH ONLY" or "FOR READ ONLY" in
DB2 SELECT statements then you will have to change the code because
ORACLE does not support "FOR FETCH ONLY" and "FOR READ ONLY".

Try to stick to SQL92 standard and it will be easy to port.

DB2 and Oracle has precompiler that converts ESQL to C function calls.

If you use CLI then each database has different Call Level Interface,
I did not find any similarity between Oracle and DB2, and you know Microsoft will
be different than rest of the world. I believe MS SQL also has ESQL
precompiler.






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I haven't lost my mind, Above opinions are mine only.
it's backed up on tape somewhere. Others can have their own.

Most applications these days are being written with stored procedures,
not embedded SQL.

Tomasz wrote:

CLI is DB2 only right?
For multiple dbms that would be ODBC right? (ODBC is similar to CLI.)

PM

"Larry" <lsedels (AT) us (DOT) ibm.com> a écrit dans le message de
news:3F3B8790.6EAB0EB8 (AT) us (DOT) ibm.com...

Tomasz wrote:
Hi Thomasz,

We have done this (Oracle, Informix, Db2 and Watcom) (don't know about MS SQL),
works fine, but you have to look out for some differences in native/sql-mappings
f.e. Oracle maps varchar to struct, db2 and informix to char* or [], returncodes,
sqlcodes will be different, so will be includes and global(!) vars, needed casts
in SQL, format (and name!) of parameter markers, input indicator variables,
filescope-uniqueness of local (ora!) function variablenames etc.

As your application, like ours, will only connect to on db-system (I suppose), a
own
preprocessing of source and headers to generate db-specific files should give you
better results than odbc.

And btw., dynamic ESQL works fine with all of them, all you have to do, is a
EXEC SQL PREPARE <statement> FROM :<var>

hth,
Wolfgang