Insert float value into table with C - c

Question

I'm trying to insert a float value into my table "measurements" in column "thera0"
Can someone help me?
I'm beginner, don't be too hard :D
This is my first try error code
passing argument 5 of ‘PQexecParams’ from incompatible pointer type [-Wincompatible-pointer-types]
PGresult *res_values = PQexecParams(conn, "INSERT INTO measurements(theta0) VALUES($1)",1,NULL,buffer_theta0,NULL,NULL,0);
char*
expected ‘const char * const*’ but argument is of type ‘char *’
const char *const *paramValues,
~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
And this is my second try error code
memory access error
float theta = 0.2;
char buffer_theta0[10];
sprintf(buffer_theta0,"%f",theta);
PGresult *res_values = PQexecParams(conn, "INSERT INTO measurements(theta0) VALUES($1)",1,NULL,buffer_theta0,NULL,NULL,0);
float theta = 0.2;
char buffer_theta0[10];
sprintf(buffer_theta0,"%f",theta);
const char * const paran[]= {buffer_theta0};
PGresult *res_values = PQexecParams(conn, "INSERT INTO measurements(theta0) VALUES($1)",1,NULL,paran,NULL,NULL,0);

Answer 1

Maybe this can help, more information is needed to reproduce the problem.
See comments inline for explanations.
Good luck!
See this discussion of how to use C to program prepared statements
The PQexecParams function creates a prepared statement and executes it. The second parameter is the SQL statement. The third parameter is the number of parameters passed. Passing NULL to the fourth parameter means that the server should figure out the parameter types. The fifth parameter is a pointer to an array of strings containing parameters. The next two parameters are only relevant with binary parameters. Passing 0 to the final parameter we obtain result in text format, 1 in binary format.
gcc -I /usr/local/opt/libpq/include main.c -L /usr/local/opt/libpq/lib -lpq
./a.out
1 'Audi' 52642 0.52642
2 'Mercedes' 57127 0.57127
3 'Skoda' 9000 0.9
4 'Volvo' 29000 0.29
5 'Bentley' 350000 0.35
6 'Citroen' 21000 0.21
7 'Hummer' 41400 0.414
8 'Volkswagen' 21600 0.216
#include <stdio.h>
#include <stdlib.h>
#include <libpq-fe.h>
void do_exit(PGconn *conn, PGresult *res) {
fprintf(stderr, "%s\n", PQerrorMessage(conn));
PQclear(res);
PQfinish(conn);
exit(1);
}
int main() {
// Data structure to hold the data going into the database
// using a variety of incoming data types, text, integer, and float
struct rawdata {
char* name;
int value;
float megaValue;
};
// These are the values to be inserted into the measurements table
struct rawdata rawtable [] =
{
{ "Audi" , 52642 , 0.52642 },
{ "Mercedes" , 57127 , 0.57127 },
{ "Skoda" , 9000 , 0.9 },
{ "Volvo" , 29000 , 0.29 },
{ "Bentley" , 350000 , 0.35 },
{ "Citroen" , 21000 , 0.21 },
{ "Hummer" , 41400 , 0.414 },
{ "Volkswagen" , 21600 , 0.216 }
};
// Here is the database connection being used
PGconn *conn = PQconnectdb("user=atl dbname=nameofdatabase");
if (PQstatus(conn) == CONNECTION_BAD) {
fprintf(stderr, "Connection to database failed: %s\n", PQerrorMessage(conn));
PQfinish(conn);
exit(1);
}
// To be more helpful to others, create the table in each example
// this allows everyone to see the table format and how it was created
// sometimes the error is in the way tables are created
PGresult *res = PQexec(conn, "DROP TABLE IF EXISTS measurements");
if (PQresultStatus(res) != PGRES_COMMAND_OK) { do_exit(conn, res); }
PQclear(res);
res = PQexec(conn, "CREATE TABLE measurements ( measure_id serial PRIMARY KEY, col1 text, col2 integer, col3 float );" );
if (PQresultStatus(res) != PGRES_COMMAND_OK) { do_exit(conn, res); }
PQclear(res);
// This is related to the ask about how to insert values into a table using PQexecParams
// This is the string that specifies the command and the params
char *sinto = "INSERT INTO measurements VALUES($1,$2,$3,$4)";
// This is the loop to change the params on each row (and provide a unique ID)
for(int i=0; i<sizeof(rawtable) / sizeof(rawtable[0]); i++)
{
// creating storage for params, not the best way (works though)
char p1[100], p2[100], p3[100], p4[100];
// prepare param input array by initializing array to params
const char *paramValues[] = { p1, p2, p3, p4 };
// initialize params for this iteration
sprintf( p1, "%d", i+1 ); // key
sprintf( p2, "'%s'", rawtable[i].name ); // text
sprintf( p3, "%d", rawtable[i].value ); // integer
sprintf( p4, "%0.6f", rawtable[i].megaValue ); // float
// make call to database server
res = PQexecParams(conn, sinto, 4, NULL, paramValues, NULL, NULL, 0);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
do_exit(conn, res);
PQclear(res);
}
// display results
res = PQexec(conn, "SELECT * FROM measurements");
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
printf("No data retrieved\n");
PQclear(res);
do_exit(conn, res);
}
int rows = PQntuples(res);
for(int i=0; i<rows; i++) {
printf("%s %s %s %s\n", PQgetvalue(res, i, 0), PQgetvalue(res, i, 1), PQgetvalue(res, i, 2), PQgetvalue(res, i, 3));
}
PQclear(res);
PQfinish(conn);
return 0;
}