Cannot execute SELECT MAX(ORA_ROWSCN) from Embedded SQL

Question

Environment : HP-UX 11.x C++ (ProC & aCC compiler) Oracle 10g )

I am unable to execute the following command from my C++ Embedded SQL code

EXEC SQL SELECT MAX(ORA_ROWSCN) INTO :scn_timestamp
FROM table_name ;

The changes i'm making are to an existing file. Following is an excerpt from the automated build script showing compiler error:

/data/tsd_oracle/hpux/10.2.0.2/bin/proc +z ireclen=200 ORECLEN=200 LRECLEN=208 code=cpp cpp_suffix=C lines=yes sqlcheck=semantics maxopencursors=10 parse=PARTIAL unsafe_null=yes mode=oracle dbms=V8 sys_include='(/opt/aCC,/opt/aCC/include/iostream,/opt/aCC/include/rw,/usr/include)' include=/data/tsd_oracle/hpux/10.2.0.2/precomp/public include=/usr/include include=/opt/aCC/include include=/opt/aCC/include/SC iname=FILENAME.PC;

Pro*C/C++: Release 10.2.0.2.0 - Production on Fri Feb 15 12:48:35 2013

Copyright (c) 1982, 2005, Oracle. All rights reserved.

System default option values taken from: /data/tsd_oracle/hpux/10.2.0.2/precomp/admin/pcscfg.cfg

Error at line 81, column 5 in file FILENAME.PC
EXEC SQL SELECT MAX(ora_rowscn) INTO :scn_timestamp
....1
PLS-S-00201, identifier 'ORA_ROWSCN' must be declared
Error at line 81, column 5 in file FILENAME.PC
EXEC SQL SELECT MAX(ora_rowscn) INTO :scn_timestamp
....1
PLS-S-00000, SQL Statement ignored
Semantic error at line 81, column 5, file FILENAME.PC:
EXEC SQL SELECT MAX(ora_rowscn) INTO :scn_timestamp
....1
PCC-S-02346, PL/SQL found semantic errors
*** Error code 1
clearmake: Error: Build script failed for "FILENAME.C"

The contents of the default option value file /data/tsd_oracle/hpux/10.2.0.2/precomp/admin/pcscfg.cfg are as follows

sys_include=(/data/tsd_oracle/hpux/10.2.0.2/precomp/public,/usr/include)
ltype=short
define=ORASTDARG

I've also tried variations of that command such as

EXEC SQL SELECT MAX(A.ORA_ROWSCN) INTO :scn_timestamp
FROM table_name A;

For which i get error saying that ORA_ROWSCN column doesn't exist.

I've verified that this sql query works in the SQLPlus console. Any particular reason why this isn't working when embedded?

---------------------------WORKAROUND-------------------------------

Based on Dominic's suggestion i was successfully able to retrieve what i wanted by using the following

EXEC SQL PREPARE timestamp_stmt FROM 'SELECT MAX(A.ora_rowscn) FROM table_name A';
EXEC SQL DECLARE timestamp_cur CURSOR FOR timestamp_stmt;
EXEC SQL OPEN timestamp_cur;    
EXEC SQL FETCH timestamp_cur INTO :scn_timestamp;   
EXEC SQL CLOSE timestamp_cur;

I'm happy with this workaround, though i still wonder why it doesn't work the usual way. I had also tried using cursors before and had the same error stating "identifier 'ORA_ROWSCN' must be declared".

Anyways, Thanks Dominic

Answer 1

have you tried wrapping it in a dynamic sql block to hide it from the pro*c compiler to see if that works?

i.e. using something like EXEC SQL PREPARE sql_stmt FROM :select_stmt; where select_stmt is your char array that contains select max(a.ora_rowscn) from table_name a