如何检查两个日期之间是否存在条目

Question

I have an sql table "flights" where there are all the details of all the flights: aircraft registration, arrival date, departure date an so on... Now when I want to create a new flight I would like to check if a flight with the same registration already exists between two given dates. EG: have a flight called IFLY arriving 22/7/2019 and departing 25/7/2019, now if I try to create another flight with the same registration but arriving 23/7/2019 and departing 24/7/2019, I would like to check in the database that during those dates another flight with the same registration is already in the database and alerting the user.

I have tried something like this: html form via jquery/ajax calling a request on the DB

$regist = $_POST['regCreate'];
$arrivalDate = $_POST['adof'];
$departureDate =$_POST['ddof'];

$sql = "SELECT reg FROM flights WHERE reg = '$regist' AND (adof or ddof) 
 >= '$arrivalDate' AND (adof or ddof) <= '$departureDate'  ";//
$data = mysqli_query($conn, $sql);

 if (mysqli_num_rows($data) > 0) {
  echo 'exists';
 }

this code is not working bacause if I create a new flight that is situated between two dates already created is not giving me the excepted result.

Answer 1

Two time periods overlap if they each begin before the other ends.

You can phrase this as:

SELECT f.reg
FROM flights f
WHERE f.reg = ? and
      f.departureDate < ? and  -- the input arrival date
      f.arrivalDate > ?        -- the input departure date

Note that I changed the syntax to use parameters. This is a best practice when devising queries in PHP or any other application layer.

Answer 2

I have founded this solution

$sql = "SELECT reg, adof, ddof FROM flights WHERE reg = '$regist' AND adof < 
'$arrivalDate' ";//
 $data = mysqli_query($conn, $sql);

if (mysqli_num_rows($data) > 0) {
 foreach ($data as $key => $v) {
  if ($v['ddof'] >= $arrivalDate) {
   echo 'exists';
   }
  }
 }