do_query error

Using Arduino Programming Questions
#1

Taken the code below, how do you loop so that the data continues to insert into the database for a specified time?

#include <SPI.h>
#include <Ethernet.h>
#include <sha1.h>
#include <stdlib.h>
#include <mysql.h>

byte mac_addr[] = { 
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress server_addr(192, 168, 2, 13);  // Supply the IP of the MySQL *server* here

char user[] = "admin";         // can be anything but the user must have
char password[] = "fmeo";   // access rights to connect (host must permit it)

// WiFi card example
//char ssid[] = "my_lonely_ssid";
//char pass[] = "horse_no_name";

Connector my_conn;        // The Connector/Arduino reference

// String constants for examples. Uncomment those you need.

const char INSERT_DATA[] = "INSERT INTO test_arduino.temps VALUES (%s, NULL)";
const char HELLO_DATA[] = "SELECT * from test_arduino.temps";

/**
 * do_query - execute a query and display results
 *
 * This method demonstrates how to execute a query, get the column
 * names and print them, then read rows printing the values. It
 * is a mirror of the show_results() example in the connector class.
 *
 * You can use this method as a template for writing methods that
 * must iterate over rows from a SELECT and operate on the values read.
 *
 */

void setup() {
  Serial.begin(115200);
  while (!Serial); // wait for serial port to connect. Needed for Leonardo only

  Ethernet.begin(mac_addr);
  Serial.print("My IP address is: ");
  Serial.println(Ethernet.localIP());
  //  }

  delay(1000);
  Serial.println("Connecting...");
  if (my_conn.mysql_connect(server_addr, 3306, user, password)) {
    delay(1000);
  }
  else
    Serial.println("Connection failed.");

  // EXAMPLE 5

  // Inserting real time data into a table.
  // Here we want to insert a row into a table but in this case we are
  // simulating reading the data from a sensor or some other component.
  // In this case, we 'simulate' reading temperature in celsius.

  float value_read = 26.9;

  // To use the value in an INSERT statement, we must construct a string
  // that has the value inserted in it. For example, what we want is:
  // 'INSERT INTO test_arduino.temps VALUES (26.9, NULL)' but the 26.9 is
  // held in the variable 'value_read'. So, we use a character string
  // formatting operation sprintf(). Notice here we must convert the float
  // to a string first and we use the %s specifier in the INSERT_DATA
  // string.

  char query[64];
  char temperature[10];
  dtostrf(value_read, 1, 1, temperature);
  sprintf(query, INSERT_DATA, temperature);
  my_conn.cmd_query(query);
}

void loop() {

}
#2 
 column_names *c; // pointer to column values
 row_values *r;   // pointer to row values

What are these lines of code intended to do ?

#3 
  if (my_conn.mysql_connect(server_addr, 3306, user, password)) {
    delay(1000);
  }

If you successfully connect, twiddle your thumbs doing nothing for a whole second.

Otherwise,

  else
    Serial.println("Connection failed.");

  // EXAMPLE 5

  // Inserting real time data into a table.
  // Here we want to insert a row into a table but in this case we are
  // simulating reading the data from a sensor or some other component.
  // In this case, we 'simulate' reading temperature in celsius.

  float value_read = 26.9;

  // To use the value in an INSERT statement, we must construct a string
  // that has the value inserted in it. For example, what we want is:
  // 'INSERT INTO test_arduino.temps VALUES (26.9, NULL)' but the 26.9 is
  // held in the variable 'value_read'. So, we use a character string
  // formatting operation sprintf(). Notice here we must convert the float
  // to a string first and we use the %s specifier in the INSERT_DATA
  // string.

  char query[64];
  char temperature[10];
  dtostrf(value_read, 1, 1, temperature);
  sprintf(query, INSERT_DATA, temperature);
  my_conn.cmd_query(query);
}

Immediately query the database. Please explain THAT logic.

  dtostrf(value_read, 1, 1, temperature);

Put one digit after the decimal point, and the decimal point, and the required number of digits before the decimal point in the array, using only one place in the array. How’s that working for you?

Taken the code below, how do you loop so that the data continues to insert into the database for a specified time?

unsigned long doneDiddling = millis();

while(millis() - doneDiddling < specifiedTime)
{
   // do whatever needs doing
}
#4