Converting double to string in Oracle pro*c - sql

Question

Is there any way to convert a double value to string without losing any digit in Oracle pro*c? The precision varies as the column from which value is fetched is NUMBER(10,8)

Answer 1

Like it was mentioned in comments you can use TO_CHAR to convert to a string. In Pro*C it would look something like this:
EXEC SQL DECLARE num_test_cursor CURSOR FOR SELECT TO_CHAR(num) FROM numtest;
Then you can fetch it into a variable:
EXEC SQL FETCH num_test_cursor INTO :number_string;
Finally with
number_string[strcspn(number_string, " ")] = '\0';
you can remove all padding space characters at the end.
Test
Create a table in an SQL client, e.g. SQLPlus, and fill it with some test entries:
CREATE TABLE numtest ( num NUMBER(10,8));
INSERT INTO numtest VALUES (99.99999999);
INSERT INTO numtest VALUES (3.141592654);
INSERT INTO numtest VALUES (0.00000001);
INSERT INTO numtest VALUES (1.23);
Complete, Self-contained Pro*C Program
exec sql begin declare section;
char *connectString = "scott/tiger#pdb";
int limit;
char number_string[11 + 1]; //number(10,8) + NUL
exec sql end declare section;
exec sql include sqlca;
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
int main(void) {
exec sql connect :connectString;
if(sqlca.sqlcode == 0) {
printf("connected to db\n");
} else {
fprintf(stderr, "failed:%s (error code=%d)\n", sqlca.sqlerrm.sqlerrmc, sqlca.sqlcode);
exit(1);
}
EXEC SQL SELECT COUNT(*) INTO :limit FROM numtest;
printf("row count: %d\n", limit);
EXEC SQL DECLARE num_test_cursor CURSOR FOR SELECT TO_CHAR(num) FROM numtest;
EXEC SQL FOR :limit OPEN num_test_cursor;
int row;
for(row = 0; row < limit; row++) {
EXEC SQL FETCH num_test_cursor INTO :number_string;
number_string[strcspn(number_string, " ")] = '\0';
printf("number as string: \"%s\"\n", number_string);
}
_getch();
return 0;
}
The debug outputs of the program confirm the desired result:
connected to db
row count: 4
number as string: "99.99999999"
number as string: "3.14159265"
number as string: ".00000001"
number as string: "1.23"