postgres random select

To perform a random select in PostgreSQL using the C language, you can use the following code:

#include <stdio.h>
#include <stdlib.h>
#include <libpq-fe.h>

int main() {
   PGconn *conn;
   PGresult *res;
   const char *conninfo = "dbname=mydb user=myuser password=mypassword";
   const char *query = "SELECT column FROM table ORDER BY RANDOM() LIMIT 1";

   conn = PQconnectdb(conninfo);

   if (PQstatus(conn) == CONNECTION_OK) {
      res = PQexec(conn, query);

      if (PQresultStatus(res) == PGRES_TUPLES_OK) {
         int num_rows = PQntuples(res);

         if (num_rows > 0) {
            int random_row = rand() % num_rows;
            const char *value = PQgetvalue(res, random_row, 0);
            printf("Random value: %s\n", value);
         } else {
            printf("No rows found.\n");
         }
      } else {
         printf("Query execution failed.\n");
      }

      PQclear(res);
   } else {
      printf("Connection to database failed.\n");
   }

   PQfinish(conn);
   return 0;
}

Make sure to replace mydb, myuser, mypassword, column, and table with the appropriate values for your database.

This code establishes a connection to the PostgreSQL database, executes the query to select a random row from the specified table, and retrieves the value from the selected row. The rand() function is used to generate a random index within the range of the number of rows returned by the query.

Please note that you need to have the PostgreSQL C library installed and linked properly for this code to work.