Can't store the values I get from my temperature in the database.

Using Arduino Sensors
9

I'm a newbie too, and I don't understand anything about your code, but this might be all you need

http://www.parallax.com/tabid/393/default.aspx

It isn't made for, but can be adapted to, Arduino. The vital serial commands look like this:

Serial.println("LABEL,Time,InTemp,OutTemp,diff,DrainTemp");

  sensors.setResolution(InThermo, 12);
  sensors.setResolution(OutThermo, 12);
  sensors.setResolution(DrainThermo, 12);

void loop() {
  running();
  GetClock();
  myFile = SD.open(filename, FILE_WRITE);//<<<<<<<<<<<<< OPEN
  if (hour == 0 && minute == 0 && second <2)
  {
    getFileName();
  }
 Serial.print("DATA,TIME,       "); 

  int ret=0;
  //get the values from the DS8B20's 
  sensors.requestTemperatures();

  float InTemp = (sensorValue(InThermo));
  float OutTemp = (sensorValue(OutThermo));  
  float DrainTemp = (sensorValue(DrainThermo)); 

  float diff = OutTemp - InTemp;

  datastreams[0].setFloat(InTemp);
  datastreams[1].setFloat(OutTemp);
  datastreams[2].setFloat(DrainTemp);
  datastreams[3].setFloat(diff);
  Serial.print(InTemp);
  Serial.print(" ,  ");
  Serial.print(OutTemp);
  Serial.print(" ,  ");
  Serial.print(DrainTemp);
  Serial.println(" ,  ");

  lcd.setCursor(49,0);
  lcd.print(InTemp);
  lcd.setCursor(49,1);