cingresembedded-sql

Ingres fetching select into SQLDA


I am trying to use Embedded SQL in C to fetch rows from an Ingres database and return the results into the SQLDA structure. I will be selecting ints, longs and strings. So far my program fetches the strings fine, but I have issues with the ints and longs.

EXEC SQL DECLARE select_string STATEMENT;
EXEC SQL BEGIN DECLARE SECTION;
   char sql[1000];
   int errorno;                /* ingres error number */
   char errortext[257];
EXEC SQL END DECLARE SECTION;
strcpy(sql, "SELECT 18, 100, 3774, 2147483647, 'dfsdfsf'");
printf("%s\n",sql);

EXEC SQL DECLARE csr0 CURSOR FOR select_string;
EXEC SQL PREPARE select_string FROM :sql;
EXEC SQL OPEN csr0 FOR READONLY;

//sqlda
IISQLDA *sqlda;
sqlda = (IISQLDA *)calloc(1, IISQDA_HEAD_SIZE + ((longs+ints+strings) * IISQDA_VAR_SIZE));
sqlda->sqln = (5);
EXEC SQL DESCRIBE select_string INTO :sqlda;

int i,j;

for( i = 0; i < sqlda->sqld; i++)
{
   printf("%d ",sqlda->sqlvar[i].sqllen);
   sqlda->sqlvar[i].sqldata = malloc(sqlda->sqlvar[i].sqllen);
   sqlda->sqlvar[i].sqlind = malloc(sizeof(short));
}
printf("\n");

EXEC SQL FETCH csr0 USING DESCRIPTOR sqlda;

for( i=0; i<sqlda->sqld; i++)
{
   printf("len:%d | ",sqlda->sqlvar[i].sqllen);
   for(j=0;j<sqlda->sqlvar[i].sqllen;j++){
      printf("%d ",sqlda->sqlvar[i].sqldata[j]);
   }
   printf(" | ");
   for(j=0;j<sqlda->sqlvar[i].sqllen;j++){
      printf("%c ",sqlda->sqlvar[i].sqldata[j]);
   }
   printf(" | %ld",*sqlda->sqlvar[i].sqldata);
   printf("\n");
}

for( i = 0; i < sqlda->sqld; i++)
{
   free(sqlda->sqlvar[i].sqldata); 
   free(sqlda->sqlvar[i].sqlind);
}
free(sqlda);

The output is as follows.

SELECT 18, 100, 3774, 2147483647, 'dfsdfsf'
2 2 2 4 7
len:2 | 18 0  |    | 18
len:2 | 100 0  | d   | 100
len:2 | -66 14  | ▒   | 4294967230
len:4 | -1 -1 -1 127  | ▒ ▒ ▒  | 4294967295
len:7 | 7 0 100 102 115 100 102  |   d f s d f  | 7

Observations: small ints (1 byte) work as expected. The information is encoded into the char array (sqlda->sqlvar[]->sqldata) in the first position. Once you try and go above 1 byte it starts to get weird. The string is cut off by 2 bytes, however if you read two more bytes into the char array the data is there, so I'm not worried about that.

What am I doing wrong / how do I properly fetch into a sqlda so that ints/longs are saved in a manner that I can retrieve them later?


Solution

  • When displaying one of the int2 values retrieved from the database, try something like: *(short *)sqlda->sqlvar[i].sqldata

    The string value 'dfsdfsf' is being retrieved as a varchar rather than a char (see sqlda->sqlvar[i].sqltype), the first 2 bytes of a varchar contain the string length.