ECPG: non-integer constant in group by

[Poul Jensen <flyvholm@xxxxxxxxx>]

I actually have two questions.

1) It seems like the fastest way to find the # of distinct elements in a 
column is using GROUP BY. With ECPG, if I try
   EXEC SQL SELECT filenm FROM beamdata GROUP BY filenm;
   I will get "sql error Too few arguments". Why? Can I correct the 
query to avoid the error message? (sqlca.sqlerrd[2] does contain the # 
of elements in spite of error)

2) The code below was meant to find the # of distinct elements for many 
columns, but fails with the message
   sql error 'non-integer constant in GROUP BY'
   thrown at the EXEC SQL EXECUTE statement. What is the problem? I 
suspect it is the definition char *vars[NVARS], but couldn't find any 
working alternatives. :-|

--------------------------

#define NVARS 24

int main(int argc, char *argv[]) {

 int i, n_occ[NVARS];

 EXEC SQL BEGIN DECLARE SECTION;
 char *vars[NVARS] = { "filenm", "yr", "mo", "dy", "hr", "mt", "sc",
             "us", "stat_id", "bmnum", "channel", "scnflag",
             "cp_id", "intt", "intt_us", "frang", "rsep",
             "tfreq", "noise", "natten", "nave", "nrang",
             "gsct", "isct" };
 char dbnm[50], *stmt = "SELECT ? FROM beamdata GROUP BY ?;";
 EXEC SQL END DECLARE SECTION;

 EXEC SQL WHENEVER SQLWARNING SQLPRINT;
 EXEC SQL WHENEVER SQLERROR SQLPRINT;

 sprintf(dbnm,"%s",argv[1]);

 EXEC SQL CONNECT TO :dbnm;

 EXEC SQL PREPARE query FROM :stmt;

 for (i=0; i<NVARS; i++)
 {
   EXEC SQL EXECUTE query USING $vars[i], $vars[i];
   n_occ[i] = sqlca.sqlerrd[2];
   fprintf(stderr,"# %s: %d\n", vars[i], n_occ[i]);
 }

 EXEC SQL DEALLOCATE PREPARE query;

 EXEC SQL COMMIT;

 EXEC SQL DISCONNECT;

 return 0;

}